Download Venereal Disease By Dr. Nazih Wayes Zaid

Venereal Disease By Dr. Nazih Wayes Zaid
2016
Venereal Diseases
Many of the infectious diseases of cattle adversely affect reproductive performance, either by direct
effects upon the reproductive system or via indirect effects upon the general state of health of affected
animals. Infectious diseases can affect the reproductive system in the following main ways:
● Impaired sperm survival or transport in the female tract, leading to reduced fertilization rate.
● Direct effects upon the embryo. This includes infections that result in early embryonic death, and those
that infect the more advanced fetus or its placenta, resulting in abortion, stillbirths or the birth of weak
calves.
● Indirect effects upon embryo survival. This includes infections that have adverse effects upon uterine
function and those that infect the maternal component of the placenta. Again, these result in embryonic
death, fetal death with abortion, mummification or stillbirth.
● Systemic illness causing fetal losses (e.g. pyrexia-induced abortion) or a direct impairment of reproductive
cyclicity.
The patterns of enzootic infectious diseases that affect reproduction have changed considerably in
most developed countries over the past 40–50 years. The classic venereal diseases, campylobacteriosis and
trichomoniasis, have been largely eradicated in dairy cattle, by the use of artificial insemination with semen
from disease-free bulls.
BACTERIAL AGENTS
Genital campylobacteriosis
Infection due to Campylobacter fetus (formerly Vibrio foetus) has long been recognized as a cause of
abortion in sheep and cattle. It should be noted that the term ‘campylobacteriosis’ has largely replaced
‘vibriosis’ in describing the disease caused by C. fetus. In dairy cows, the importance of the disease has
declined over the past 40 years with the use of artificial insemination, because of bull screening at artificial
insemination studs and the use of antibiotics in semen extenders. It is still a major cause of reproductive
disease in many countries. Saprophytic organisms such as C. bulbus and C. faecalis may be present in the
alimentary tract of cattle and in the prepuce of the bull.
Clinical signs and course of disease
The bull normally carries the infection for life without any interference with its reproductive
behavior or seminal qualities. The organism is confined to the glans penis, prepuce and distal urethra, but
there are no lesions associated with the presence of the organism at any of these sites. Thus, the bull acts
simply as a mechanical carrier and transmits the infection at service to the female. The sites of infection in
the cow are the vagina, cervix, uterus and uterine tubes. Within the uterus, it causes a mild endometritis.
Inflammation of the cervix may also occur, causing an increased secretion of mucus which may become
mixed with uterine exudates to form a mucoflocculent vulval discharge after service. Therefore, in a
majority of susceptible females served by an infected bull, fertilization occurs but is followed by early
embryonic death. In a much smaller proportion of infected cows, later abortion occurs between 4 and 7
months. When infection is introduced into a susceptible herd, a dramatic decrease in pregnancy rate occurs.
Embryonic deaths may occur before the maternal recognition of pregnancy, in which case return to oestrus
occurs 3 weeks after service. Embryonic deaths occurring after recognition of pregnancy result in later,
irregular return to estrus, often between 25 and 35 days after service. Immunity to the organism slowly
develops and, as it does so, cows conceive and remain pregnant. Eventually, after an average of five
services, the majority of cows become safely pregnant and carry their calves to term. The majority of the
abortions due to C. fetus occur between the fourth and seventh months of gestation. Placental lesions are
very similar to, although less severe than, those caused by Brucella abortus. Typically, there is necrosis,
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with yellowish brown discoloration of the fetal cotyledons and leather-like thickening or edema of the
intercotyledonary allantochorion.
Diagnosis
Genital campylobacteriosis will be strongly suspected when a majority of cows or heifers are
returning regularly or irregularly to service, especially if the infertility coincides with the introduction of a
new bull. A variety of diagnostic tests can be used to diagnose C. fetus infection. These are:
● identification of the organism in preputial Washings direct smears, culture and fluorescent antibody tests
● serological tests
● vaginal mucus agglutination.
In bulls suspected of infection, preputial washings or scrapings of the penile or preputial mucosa can
be examined. Preputial samples from suspect bulls and material derived from aborted fetuses can be
examined using direct culture or fluorescent antibody techniques. Tissues from an aborted fetus (lung,
spleen, liver) and abomasal fluid should be removed aseptically and maintained at 4°C until they reach the
laboratory. Direct smears of abomasal contents can be examined using phase contrast or dark field
microscopy. Serological tests are of little or no value, since genital campylobacteriosis does not engender
measurable serum antibody levels. It is important to ensure that sufficient time has elapsed since animals
would have been exposed to infection; thus in investigating a herd it is important to ensure that all nonpregnant cows that were first exposed to service more than 60 days previously should be sampled.
Treatment and control
Control is based on three epidemiological facts:
● Transmission is venereal.
● Bulls remain permanently infected.
● Infected cows overcome the infection, or become immune, in a period of 3–6 months from service.
Thus, a ‘self-cure’ of the cows will occur if natural service by infected bulls is replaced by artificial
insemination. Artificial insemination (AI) is a highly effective means of control, since incoming uninfected
animals do not contract the disease and infected animals eventually become immune. Removal of bulls from
the herd prevents further venereal transmission of the disease. As C. fetus is sensitive to streptomycin this
antibiotic has been used to treat the disease in bulls. Dihydrostreptomycin, at a dose rate of 22 mg/kg
subcutaneously, together with the local application of the same antibiotic to the penis and prepuce, is
effective, although it must be remembered that the bulls will be susceptible to reinfection. An oily
suspension of procaine penicillin and streptomycin for intrapreputial infusion was used to treat or
prophylaxis of campylobacteriosis in bulls. Combination of neomycin and erythromycin, in a waxy base, is
effective in eliminating C. fetus from bulls in which streptomycin has been ineffective. Vaccination
programmers have been successful in controlling the disease in situations where artificial insemination
cannot be practiced. Using oil adjuvant bacterins with high cell counts of immunogenic strains of C. fetus
venerealis, good results have been obtained. Vaccination should preferably be carried out 30–90 days before
breeding commences and, since the immunity wanes annually, revaccination is recommended for optimum
protection as close to the time of service as possible.
Brucellosis (contagious abortion)
Brucellosis in cattle is most commonly caused by Brucella abortus. Brucella melitensis, which
occurs in sheep and goats, can also be transmitted to cattle. Brucella causes abortion in the second half of
pregnancy, together with metritis and retained fetal membranes (RFM). In bulls, it can cause orchitis,
epididymitis, seminal vesiculitis or infection of the ampullae. Because of the enormous losses that the
disease causes to dairy and beef cattle industries, it has been the subject of eradication schemes in many
countries.
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Epidemiology
Cattle can become infected by ingesting B. abortus from contaminated pasture, food or water.
Infection may occur by licking an aborted fetus, infected afterbirth or genital exudates from a recently
aborted or recently calved cow. It may even occur through the teat by infected milk of another cow, or
through the vagina by infected semen. Infected cows often shed the organism in the milk, thereby
endangering public health. Contaminated milk also provides a source of infection for calves, although the
main danger of spread to other cattle is at the time of abortion or parturition. The organism colonises the
udder and supramammary lymph nodes of non-pregnant animals. In pregnant animals, production of
erythritol within the placenta allows rapid multiplication of the bacteria, leading to endometritis, infection of
cotyledons and placentitis. The fetus is aborted 48–72 hours after death, by which time a degree of autolysis
has occurred. The fetal membranes are very frequently retained. For a day or two before, during and for
about a fortnight after abortion the genital discharge of the infected female is highly infected. When the fetal
membranes are retained, the uterus may not free itself of infection until about a month after delivery. After
the completion of uterine involution, the organisms colonies the udder and supramammary lymph nodes,
whence, in the next gestation, infection of the placenta may again occur. Outside the animal body B. abortus
thus, most herd outbreaks have been caused by the introduction of carrier animals.
Clinical signs
The disease causes serious economic loss, primarily due to abortion in the second half of gestation,
although earlier abortions occur at the beginning of an outbreak. In addition, some calves will be born alive
but they will be weak and unthrifty. Infected cows usually abort once and seldom more than twice, although
in subsequent pregnancies the uterus may be reinfected from the udder even though the cow carries the fetus
to term. RFM is more common in cows that abort in later gestation and those that carry to term. Such
animals show delayed involution of the uterus, and are prone to secondary bacterial invasion with resultant
puerperal metritis.
Diagnosis
The organism can be identified in stained smears prepared from suspected contaminated material.
Special staining techniques using a modified Koster and Ziehl-Nielson method are quite successful. A more
specific method of direct identification is a fluorescent antibody technique, which enables differentiation
from other infectious diseases such as Q fever. B. abortus can be cultured from the fetal stomach of an
abortus, or from fresh afterbirth, or uterine exudates. Because culture of the organism is time-consuming and
expensive, alternative methods of identification have been devised. A colony blot ELISA using monoclonal
antibodies provides a rapid, inexpensive and reliable method of identifying B. abortus. Numerous
serological tests have been used to diagnose brucellosis, using a wide range of biological materials such as
milk, whey, serum, vaginal mucus and semen. These have then been subjected to agglutination test,
complement fixation test, antiglobulin test, fluorescent antibody test and immunodiffusion or
electroimmunodiffusion tests. The rose Bengal plate test was introduced as the main initial screening test of
serum samples in the brucellosis eradication scheme. The milk ring test, which detects Brucella antibodies
in milk, is very useful in screening the presence of brucellosis in herds by collecting bulk milk samples or in
individual animals.
Control
Brucellosis is not only a cause of abortion in cattle, but it also causes a serious disease, undulant
fever, in man. Hence, control of the disease has to be directed at both its animal health and its public health
aspects. From the animal health viewpoint, abortions can be prevented in herds by calfhood vaccination,
using the B. abortus S19 live antigen.
Vaccination. S19 vaccine was officially introduced is a smooth variant of a strain of B. abortus, of reduced
virulence but of high antigenic quality. It was intended for use on calves before the onset of puberty. The
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ages at which calves have had to be vaccinated have varied between schemes, typically vaccination occurs at
some time between 2 and 10 months of age. Cows should be revaccinated after their first calving.
Eradication. Eradication can be undertaken by testing and slaughter of seropositive animals. In order to
undertake such a scheme, statutory powers are usually required to implement a compulsory programmer.
The main facets of a brucellosis eradication scheme are:
● Positive identification of cows and their calves.
● Traceable movements of cattle, so that potential carriers and in contact animals can be found.
● Secure boundaries to individual farms or to eradication areas are also needed, in order that uncontrolled
movements of animals are prevented.
● Regular testing of all cows, followed by immediate slaughter of reactors. For dairy cows, periodic blood
tests can be augmented by continuous monitoring of bulk milk.
● Isolation and testing of any cows that abort or have premature calving.
Leptospirosis
Leptospirosis is an important zoonotic disease of cattle and other mammals which is caused by
pathogenic spirochaetes of the species Leptospira interrogans. Distribution of the organism is world-wide
and cattle can be infected by several servers that have specific effects upon the genital system, causing fetal
death, abortion, stillbirth and weakly live calves. The spirochaete was isolated from the vagina in 21.7%, the
ovary and tubular genital tract in 57% and the urinary system in 62% of the animals. Leptospirosis is also of
considerable public health importance, as it causes a zoonotic disease in man. The risk of human
leptospirosis was considered of such significance that various programmers were introduced to limit the
spread of the disease to humans.
Clinical syndromes
Infection can enter via skin abrasions or through the mucous membranes of the eye, mouth or nose. It
can also be transmitted in semen after natural service or AI. After infection, a short latent period (5–14 days)
is followed by a bacteraemia, which persists for about 4–5 days until the animal mounts a immune response
against the leptospires. Thereafter, the organisms localize in tissues that are inaccessible to antibodies,
notably the kidney tubules, cotyledons and fetus. The consequence of colonisation of the kidney is a variable
period of excretion of leptospires in the urine, providing a source of environmental contamination and of
direct infection both of other cows and of humans. Renal damage can be severe, which is more serious in
non-maintenance hosts than in maintenance hosts. Likewise, other pathological changes, such as haemolysis,
nephritis and hepatitis, can be serious in non-maintenance hosts. Leptospires can be present in puerperal
discharges for up to 8 days, and can persist in the pregnant and non-pregnant uterus for up to 142 and 97
days after infection, respectively. The demonstrate leptospires subgroup sejroe in the genital tracts of bulls,
vesicular glands, as well as the urinary system. Venereal transmission is thus a possibility. Clinical
syndromes include:
● An acute febrile disease, characterized by temperatures of 40C or more, together with haemoglobinuria,
icterus and anorexia. Leptospiral mastitis may also be present. This syndrome is usually caused by strains
such as pomona, canicola, icterohaemorrhagiae and grippotyphosa. Deaths may occur, especially in calves,
and there may be abortions.
● A less acute type of disease where there is no pyrexia; this is most frequently associated with hardjo. The
resultant reproductive effect of infection with L. hardjo is abortion, stillbirth or the birth of weakly calves.
Abortion can occur at all stages of gestation from the fourth month to term; it is most common after 6
months. It can occur in the absence of any clinical signs of disease, but can also be accompanied by
leptospiral mastitis or the ‘flabby bag’ milk-drop syndrome.
● Leptospiral mastitis and milk-drop syndrome. In some herds, abortions have occurred after a ‘leptospiral
mastitis’ or agalactia has been observed during the previous 3 months. Infection causes a bacteraemia with
or without a concurrent pyrexia. There is a precipitous fall in milk yield, especially in cows that are in early
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lactation. From all four quarters the milk that is obtained is thick and colostrums like with clots, and is
frequently blood-tinged. The udder is soft and flaccid. Agalactia lasts about 2–10 days, after which milk
production usually returns close to normal although, in cows near the end of their lactation, milk production
may not recover.
Dairy heifers usually become infected at 2–3 years of age, either from older cows or an infected bull.
Diagnosis
There are no lesions that are specific for leptospirosis; thus diagnosis of leptospirosis as a cause of
abortion is based almost entirely upon demonstrating specific antibodies in fetal sera or by demonstrating
leptospires in fetal organs, particularly lungs, kidneys and adrenal glands, by culture or
immunofluorescence. The MAT is used extensively in the diagnosis of leptospirosis, using serum from
animals that have aborted or are suspected of being infected.
Treatment and control
General control measures related to good hygiene, thus minimizing the risk of infection with
leptospires from other host species, should be implemented. These include the strict segregation of cattle
from pigs, rodent control and the draining or fencing off of contaminated water sources. There are two
methods of specific treatment and control: the use of a vaccine or parenteral
streptomycin/dihydrostreptomycin, or a combination of both. The antibiotic should be used at a dose rate of
25 mg/kg by intramuscular injection with no greater a volume than 20 ml at any one site. Milk should be
withdrawn for 7 days and meat for 28 days. Repeated doses may be necessary. Streptomycin is effective in
clearing Pomona from the urine of infected cattle and treatment with antibiotic plus vaccination has been
effective in arresting the progress of an abortion storm. Dihydrostreptomycin is less effective in treating
hardjo, for which other antibiotics may be preferable. Vaccination of all members of the herd should be
done annually. In open herds, the frequency should be increased to 6-monthly intervals; this is particularly
important for heifers between 6 months and 3 years of age.
Haemophilus somnus
Haemophilus somnus is a fairly common inhabitant of the genital tracts of male and female cattle.
The strains of H. somnus that infect cattle are different from those which cause disease in sheep. The
organism can be routinely isolated from the mucosal surfaces of the urogenital tract of normal healthy cattle,
in the absence of any macroscopic lesions. In the literature the organism has been isolated from 28% of
normal cows and 90% of normal bulls. H. somnus infection in cattle causes septicaemia, polyarthritis,
pneumonia/pleurisy and thrombotic meningoencephalitis. It has been reported to affect reproduction
adversely in a number of different ways. It causes abortion, endometritis, vaginitis and cervicitis. It may also
be one of the organisms responsible for granular vulvovaginitis. Most commonly, the bull is asymptomatic,
but the organism can cause testicular degeneration or even frank orchitis. H. somnus also causes bovine
epididymitis, producing a large, multiloculated abscess, usually within a single epididymis. Diagnosis can be
made following culture of the organism. Serological tests are currently unreliable. In aborted fetuses, lesions
are scanty and non-specific. Lesions of the placenta occur mainly within the cotyledons, consisting of an
acute, non-suppurative placentitis. Penicillin and streptomycin have been reported to have been used
successfully in treating cows where H. somnus was frequently isolated from cervico-vaginal mucus, and
where fertility was depressed. Since the organism colonises the genital tract of the bull and can be isolated
from semen, this may well be an important source of infection of cows and heifers. Good hygiene and the
use of combinations of antibiotics should control infection following artificial insemination.
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MYCOPLASMA, UREAPLASMA AND ACHOLEPLASMA INFECTIONS
Mycoplasma
Mycoplasma bovigenitalium was demonstrated in the genital tract of infertile cows and the semen of
bulls. The two species which appear to be of greatest importance in cattle are M. bovigenitalium and M.
bovis. M. bovigenitalium is found in the vaginal mucus of normal and Repeat Breeder cows, which has led
to speculation concerning its role as a pathogen. The organism may also cause granular vulvovaginitis,
although spread of the organism from infected bulls and resultant infertility have also been demonstrated. M.
bovigenitalium also inhabits many parts of the reproductive tract of the bull. It has been suggested that the
prepuce and urethral orifice are the primary locations of the organism, but it has also been recovered from
virtually every part of the male tract. It has been isolated from 15 to 32% of semen samples. It has been
implicated as a cause of seminal vesiculitis, as it both is isolated frequently from clinical cases and can
infect the vesicular glands after experimental inoculation. When it infects the testes or epididymides,
M.bovigenitalium may cause detrimental changes to semen quality, especially after cryopreservation. M.
bovis causes mastitis in adult cattle and polyarthritis in calves. It is a successful pathogen of the uterus,
causing extensive lesions of the uterus, uterine tubes and even peritonitis. It persists in the uterus and vagina
for long periods (1 and 8 months, respectively) after infection. M. bovis has been shown to cause abortion in
both natural and experimental infections. Since it is seldom found in the reproductive tract of normal cows,
isolation of the organism from the placenta or aborted fetus can be considered significant. M. bovis is found
in bovine semen less often than M. bovigenitalium and its pathogenicity for the bull has not been
established. Other Mycoplasma species (e.g. M. bovirhinis, M. arginini, M. alkakescence, M. canadense and
M. gallisepticum) have been isolated occasionally from abortuses, but for these, as well as for M.
bovigenitalium, the evidence for being the initiating cause of abortion is not clear-cut, since mycoplasmas
have frequently been isolated from spontaneously aborted fetuses.
Ureaplasma diversum
Ureaplasma diversum is a common inhabitant of the genital tract of the cow. It persists only briefly
in the uterus and uterine tubes, but is most commonly found in the vagina and vestibule. Acute infection
produces granules around the clitoral region and on the lateral walls of the vagina, which are accompanied
by hyperaemia of the vulva and a profuse, mucopurulent vaginal discharge. Large, purulent lesions may also
be present. These may give way to less obviously inflamed, chronic lesions. U. diversum can also produce
endometritis and salpingitis. These lesions have been associated with high levels of embryonic death and
returns to oestrus, which are accompanied by a mucopurulent vaginal discharge. Abortions may also occur,
but Ureaplasma may often be isolated as an incidental finding from calves that have been aborted for other
reasons. U. diversum can infect the penis and prepuce of the bull and has occasionally been isolated from all
parts of the male tract. It is generally regarded as non-pathogenic in the male, although some have attributed
low-grade lymphoid granulomas on the penile integument to the presence of the organism. The main means
of transmission of the infection is by the venereal route. Infected semen used in AI seems of particular
importance, since its deposition into the uterus allows the development of chronic endometritis, rather than
of acute vulvovaginitis.
Acholeplasma
Three species of Acholeplasma have been isolated from cattle: A. modicum, A. laidlawii and A.
axanthum. Of these, A. laidlawii has been isolated most often, largely from the bull. It is possible that
Acholeplasma infection of cows may cause pathological changes in the genital tract, but the case is far from
proven. It is often isolated from aborted calves, but as described above, may not be the causal organism. It
probably causes no pathological lesions of the bull.
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Diagnosis
Most bovine mycoplasmas are easily recovered in conventional mycoplasma media, although some
may require special supplements or conditions for optimum growth.
Treatment and control
Natural service, if used, should be suspended and semen should be collected and cultured for the
presence of mycoplasmas. Instead, animals should be inseminated with semen that is known to be free of
contaminant organisms. Infected bulls should be rested for 3 months and treated systemically for 5 days with
tetracycline's, together with sheath irrigation. A number of antibiotics have been incorporated in semen for
the control of these organisms. A combination of lincomycin, spectinomycin, tylosin and gentamycin added
to raw semen, and non-glycerolated whole milk or egg yolk-based extenders has been shown to control M.
bovis, M. bovigenitalium and Ureaplasma spp.. If artificial insemination is used, the standard Cassou pipette
should be protected by a disposable polythene sheath to prevent vulval or vaginal contamination before it is
introduced through the cervix. The uterus can be infused with a solution containing 1 g of tetracycline or
spectinomycin 1 day after insemination, a treatment that has been shown to improve pregnancy rates.
PROTOZOAL AGENTS
Trichomoniasis
The recognition of Trichomonas (Tritrichomonas) fetus infection as a cause of infertility was an
important advance in our understanding of the role of specific venereal pathogens in cattle. Hence, whenever
natural service is used, trichomoniasis must not be overlooked as a cause of infertility.
Clinical signs
Trichomoniasis is a classic venereal disease that is transmitted to cows from asymptomatic carrier
bulls during coitus. The causal organism is a flagellate protozoan.
The bull. Bulls become infected by serving an infected cow. The infection rate from cows to bulls is high;
about 50% of bulls become infected from one service of an infected cow. Bulls can remain infected for life,
remaining asymptomatic throughout. Interestingly, however, some bulls have also proved highly resistant to
infection; about 20% of bulls failed to become infected after numerous mating with infected cows. It is also
evident that younger bulls are less liable to become persistent carriers than are older bulls. The organism
lives within the crypts and folds of the penile integument and preputial mucosa. Control of trichomoniasis
through AI can only be achieved if the stud bulls are free of the disease, since trichomoniasis can also be
spread from bull to bull via contaminated artificial vaginas.
The cow. Although the number of trichomonads needed to establish an infection in the cow is large,
transmission rates are high. In addition to natural service, cows can be infected via insemination with
contaminated semen. Rarely, infection can occur following the use of contaminated instruments such as
vaginal specula. In the cow, T. fetus colonises the uterus, cervix and vagina, but it survives poorly on the
vulva. Within the uterus, the organism produces a catarrhal endometritis and vaginitis, with oedema of
vulva, perivaginal tissue and uterine wall. The disease does not prevent fertilization, but causes embryonic
death at an early stage of gestation. Typically, embryonic death occurs after the maternal recognition of
pregnancy (day 16), causing an irregularly extended return to estrus, although some animals exhibit normal,
or even short, returns to estrus. Many pregnancies fail at between 30 and 50 days of gestation. Embryonic
death is not infrequently (up to 10% of cases) accompanied by the development of pyometra, in which the
uterus is filled with enormous quantities of trichomonad-filled, thinnish pus. Vaginal discharge of this pus is
common. Some abortions occur between the second and fourth months of gestation, but very few occur after
the fourth month. In later-term abortions, trichomonads can be found in the chorion, fetal lung and fetal gut.
The fetus is smaller than that appropriate to the period of gestation. Parasites quickly disappear from the
vaginal discharges after abortion (usually within 7 days). Hence cows and heifers, which have been exposed
to infected service, fall into the following clinical groups:
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● become pregnant and carry to term without clinical signs of infection developing
● return to multiple services, but show no obvious signs of infection; estrous cycles may be regular or
irregular
● fail to become pregnant and develop an oedematous condition of the endometrium with a mucoflocculent
discharge
● become pregnant, but abort at 2–4 months of gestation.
● develop pyometra and become acyclic.
Diagnosis
Diagnostic samples. Although clinical signs and history may be strongly supportive of a diagnosis of
trichomoniasis, diagnosis in the female cow is best achieved by demonstrating the presence of trichomonads
in uterine pus, vaginal discharges, cervical mucus or abortus material. The best source of material is the fetal
membranes or the organs of an aborted fetus (especially the abomasum). Elimination rates of infection are
highly variable after an infected mating, so failure to demonstrate the presence of the organism does not
necessarily imply its earlier absence. Material contaminated with faces should be discarded, because nonpathogenic trichomonadlike organisms may be present. In the bull, diagnosis is made by the collection of
preputial scrapes or preputial washes. Vigorous scraping of the preputial mucosa. The bull should be
allowed a period of 5–10 days of sexual rest before sampling so that the number of trichomonads can
increase.
Demonstration of the organism. Whatever the source of the material which might contain trichomonads, it
should be examined as soon as possible after collection. Preputial washings are centrifuged in order to
concentrate the organisms. Various media can be used for culture, including:
● trypticase-yeast extract-maltose (TYM)
● Diamond’s medium (TYM + 1% agar); for this method, an incubation period of up to 9 days is required
● In Pouch system. Organisms are visualized after culture.
Various methods have been developed in an attempt to increase the efficiency of diagnosis of
trichomoniasis, including immunohistochemistry and polymerase chain reaction. Agglutinating antibodies
are developed locally in the vagina and uterus in response to infection; their identification can be used as a
herd test in the same way as described previously for C. fetus.
Treatment and control
Control can be attempted by:
● eliminating bulls and replacing natural service by AI
● ‘active’ management of groups of cows and use of bulls
● treatment and/or vaccination of cows and bulls.
Artificial insemination. Control through artificial insemination (AI) is based upon the assumption that
recovery in the female is spontaneous, and that infection of healthy animals cannot occur if natural service is
replaced by AI with semen from non-infected bulls.
Group management. Many different ideas have been suggested as ways of managing trichomonad-infected
herds without resorting to the total use of AI. In principle, when it is established that T. fetus infection exists
in a herd, the females should be grouped as follows:
● those which are definitively known not to have been exposed to infection. This group will comprise
maiden heifers and any recently calved cows that have not been served since the introduction of an infected
bull
● all other cows whose disease-free status is not definitively established. All bulls on the farm should be
regarded as being infected, unless individuals’ disease-free status is beyond debate.
The ‘clean’ group (Group 1) is bred to known uninfected bulls. The other group can be bred to any bull until
they conceive, after which those bulls are eliminated. After a full-term pregnancy the Group 2 cows should
be free of infection.
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Treatment. As a general principle, carrier bulls should be culled since, unlike the infection in the female, it
persists indefinitely. Treatment of the bull can be attempted by the use of topical substances infused into the
prepuce or applied to the penis. Iodine-based compounds, acriflavine and imidazoles have all been used.
Systemic treatment was first attempted by used sodium iodide at a dosage of 5 g/45 kg body weight in 500
ml water, by intravenous injection on five occasions at 2-day intervals. More recently, treatment with
imidazoles has been reported as both feasible and effective. Dimetridazole can be given orally (50 mg/kg per
day for 5 days. Ipronidazole can be used, but has to be preceded by the use of broad-spectrum antibiotics to
kill non-specific bacteria in the prepuce that break down the imidazole. Cows with pyometra may be
induced into estrus with prostaglandin F2α.
Vaccination. Many attempts have been made to develop a vaccine against T. fetus. Initial work used killed
trichomonads in a mineral oil adjuvant, which helped eliminate infection from bulls. Efficacy of
trichomonas vaccines is estimated to be, at best, 60%.
VIRAL AGENTS
Bovine viral diarrhoea (BVD)
BVD was initially recognized as a cause of diarrhea during the 1940s. Although it was originally
considered to be a simple virus-induced diarrhoea, more recent understanding of the infection has shown
that it also causes infertility. BVD was first recorded as a cause of abortion in cattle. The BVD virus is a
Pestivirus, which is related to the viruses of Border disease of sheep and classical swine fever. There are two
main biotypes: a cytopathic and a non-cytopathic strain.
Transmission and pathogenesis
Infection with the non-cytopathic strain in utero between about days 30 and 125 of gestation leads
to the birth of a calf that is persistently infected with the virus. Such calves are immunotolerant and, if they
are subsequently infected with the cytopathic strain of BVD, they may develop mucosal disease. Persistently
infected animals shed the virus throughout life. The incidence of persistently infected calves (carriers) is
about 1 per 100–1000 calves born, but such animals are a major source of infection and are important in
maintaining the BVD virus in nature. Persistently infected cows can transmit the disease vertically through
transplacental infection to their calves, although the majority of persistently infected calves are born to
normal cows that were susceptible to infection during the first 4 months of gestation. Animals that are
persistently affected, or have acute infections, shed large amounts of virus in occulonasal discharges, saliva,
urine and faeces. Infection of cows at other stages of pregnancy causes early embyronic death and abortion,
with aborted fetuses exhibiting abnormalities of the central nervous and ocular systems. Infection in the last
third of pregnancy does not cause immunotolerance, but results in the birth of a calf that is immune to the
disease. Infection of susceptible adult animals that are not immunotolerant produces a transient disease,
which is characterised by a period of pyrexia plus a leucopenial viraemia that persists for up to 15 days. In
susceptible herds, there will be diarrhoea, with a high morbidity but low mortality rate, occulonasal
discharge and mouth ulcers. There is usually a drop in milk yield in dairy cows. The virus has a profound
immunosuppressive effect, which can increase the susceptibility of the host to other diseases. Bulls have
been shown to excrete the virus in their semen following spontaneous, persistent and chronic infection. The
disease is characterized by pyrexia, anorexia, watery diarrhoea, nasal discharge, buccal ulceration and
lameness. The morbidity rate is generally low, but, amongst affected animals, the mortality rate is high.
Effects upon reproductive performance
The effect of the BVD virus on reproduction depends upon the stage of pregnancy at which the cow
becomes infected. Acute infection, with either biotype, can severely affect the embryo or fetus. During the
first month of gestation, infection results in the death and resorption of a high proportion of embryos. The
only signs of reproductive disease that such affected cows or heifers exhibit is returning to estrus at normal
or extended intervals. Pregnancy rates are therefore reduced in affected animals. Low pregnancy rates also
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result from the insemination of semen that is contaminated with BVD virus, whether by AI or natural
service. BVD can also be transmitted through viruscontaminated embryos. From the second to the fourth
month of gestation, infection may be followed by abortion, death with mummification, growth retardation,
developmental abnormalities of the central nervous system and alopecia; some infected cows or heifers will
carry calves to term, but these may well become persistently infected. From the fifth and sixth months of
gestation, there can be abortion or the birth of calves with congenital abnormalities of the central nervous
system and eyes. Typically, there is a time interval of between several days and 2 months between infection
with BVD virus and abortion. However, fetal infection can also be followed by the birth of normal
premature live, stillborn or weakly calves, as well as those with congenital abnormalities.
Diagnosis
Some histological lesions are characteristic of the infection. The virus can be isolated from the fetus,
particularly lymphoid tissue such as the spleen. Immunocytochemical identification of BVD viral proteins in
fetal tissue, especially kidney, lung or lymphoid tissue, can sometimes be detected. In the case of live calves,
serum must be obtained before colostrum is ingested.
Control
This can be expensive and may not be cost-effective if it requires extensive culling of persistently
infected animals. The basic principles are that farms do not breed from persistently infected cows. Since
there is some suggestion that cross-infection can occur between cattle and sheep and goats, the species
should be separated. Vaccines are used in many countries as a control measure. Killed-virus vaccines can be
used in pregnant cows.
Infectious bovine rhinotracheitis (IBR) virus
Infectious bovine rhinotracheitis virus (bovine herpesvirus; BHV-1) is present world-wide and
causes an acute respiratory disease of cattle with conjunctivitis. It also causes a disease of the genital organs
of the bull and cow, a syndrome that has been recognized for many years, long before the respiratory form
of the disease was described or the causal organism identified. The disease of the genital system has been
variously called infectious pustular vulvovaginitis (IPV), vesicular venereal disease and coital vesicular
exanthema. BHV-1 causes both the respiratory and genital forms of the disease. BHV-1 also causes
abortion, more commonly after the respiratory, rather than the genital, form of the disease. BHV-1 infection
is also associated with infertility in cows and heifers.
Pathogenesis and transmission
The genital form of the disease (IPV) is readily transmitted venereally, but this is not the only route,
since it can occur via contaminated bedding and the mutual licking and sniffing of the vulva and perineum
of infected and non-infected animals. Also, it can be transmitted by virus contaminated semen. Once it has
gained entry, it is transported haematogenously in leucocytes. Some animals can become lifelong latent
carriers of the virus, despite the formation of specific antibodies. The infection enters a latent phase in the
ganglion cells of the nervous system. Under certain circumstances, such as stress, calving, transportation,
vaccination or corticosteroid therapy, the latent infection can be reactivated so that the virus migrates along
nerves to the periphery, where it multiplies and is excreted. These animals represent a reservoir of the virus.
Clinical signs
Infectious pustular vulvovaginitis. The onset of vulvovaginitis is sudden and acute. Signs appear 24–48
hours after venereal transmission; heifers tend to be more severely affected than cows. The vulval labia
become swollen and tender and, in light-skinned animals, deeply congested. This is quickly followed by the
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development of numerous red vesicles on the mucosa. These may rapidly rupture or develop into pustules
which give rise to haemorrhagic ulcers, 3 mm or so in diameter. The quantity of vulval discharge is variable,
ranging from small quantities of exudates, which adhere to the vulval and tail hairs, to a copious
mucopurulent discharge. A speculum is useful to examine the vaginal mucosa but, because of the pain and
discomfort, caudal epidural anesthesia is worthwhile. The lesions are obviously painful since affected
animals are restless, with swishing of the tail, frequent urination and straining. There may be transient
pyrexia and reduced milk yield, but the systemic effects are variable depending upon the presence of
respiratory problems. The acute phase of the disease will subside in about 10–14 days, but a few animals
will display a persistent vulval discharge for several weeks. When females show signs of IPV, the bull must
be examined for the presence of lesions, since, unlike the situation with most venereal diseases of cattle, the
signs in the bull are dramatic.
Infertility. Opinions have varied over the role of BHV-1 as a cause of infertility. If semen infected with the
virus was used for artificial insemination, there were reduced pregnancy rates, endometritis and shortened
interoestrous intervals. When virus-infected semen is introduced into the uterus, as would occur at artificial
insemination, infertility (i.e. poor pregnancy rates) occurs. When infected semen is deposited in the uterus it
causes a severe, necrotizing endometritis, but lesions remain localized to the site of virus deposition and
resolve in 1–2 weeks. Inoculation of IBR virus into the uterus causes endometritis, it was likely to be a cause
of infertility. Thus, artificial insemination of contaminated semen is undoubtedly associated with embryonic
death; however, the evidence for such an effect of natural service by an infected bull is less clear-cut. The
virus can affect a number of other aspects of reproduction. It can cause a bilateral necrotizing oophoritis, to
which the corpus luteum appears particularly susceptible, especially during the first few days after ovulation.
This damage to the developing corpus luteum may directly affect its function, perhaps resulting in lower
than normal progesterone production. In consequence, the survival of the embryo would be compromised.
The virus can also directly cause embryonic death, by direct invasion of cells. The consequence is
embryonic death, with the cow returning to estrus at a normal interval after insemination after infection of
heifers at the time of breeding.
Abortion. IBR virus is an important cause of bovine abortion. BHV-1 was responsible for 5.4% of abortion.
Abortion is a common sequel to infection, with or without previous respiratory tract signs of disease. The
age of gestation at the time of infection appears to be critical, since cows that are 5 1–2 months pregnant, or
less, do not abort, whilst those older than this have a 25% probability of aborting. In beef herds, abortion
‘storms’ occur, with between 5 and 60% of cows aborting. Abortions occur from 4 months of gestation to
term. Some calves are stillborn, and a few may be born alive, but succumb subsequently. The effects of virus
infection may be due to the strain of the virus. All heifers developed fever and viraemia within 2–5 days
after inoculation. On the other hand, abortion can occur with little or no accompanying respiratory or ocular
signs, or, because the interval between infection and abortion can be protracted, earlier signs of IBR
infection are not always readily associated with later abortions. The time interval from infection to abortion
varies from a few days to 100 days. In However, even in such cases, diagnostic lesions are generally present
in the fetal liver and adrenal.
Epivag. ‘Epivag’ is a specific bovine venereal disease causing epididymitis and vaginitis in cattle. In cows,
it causes diffuse infection of the vagina, but not the presence of distinct lesions as occur with IPV. A severe
mucopurulent vaginal discharge may be present during the earlier stages of the disease. Most infected cows
fail to conceive to service, but most eventually recover. About 15–25% of animals become sterile, due to the
presence of lesions of the uterine tubes, such as adhesions, hydrosalpinx, and ovarian and bursal adhesions.
Likewise, some cows develop parametritis as a result of Epivag infection, and adhesions may be widespread
throughout the pelvis and even extend into the abdomen. Most bulls have a mild balanoposthitis after
infection, although, since this is far less severe than IPV infection, it may not be observed. Subsequently,
most bulls develop an indurations of the epididymis, particularly of its tail. Orchitis may occasionally occur.
The causal organism has not been definitively characterized.
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Diagnosis
The genital tract lesions of IPV are fairly characteristic of the disease, but must be differentiated
from granular vulvovaginitis due to Ureaplasma spp. and catarrhal vaginocervicitis. Some investigators
consider that a severely autolysed fetus strongly suggests BHV-1 infection. There is frequently a
liquefactive necrosis of the whole of the kidney cortex with peri-renal haemorrhagic oedema. Histologically,
there is always focal necrosis of the liver and in many cases there are necrotic lesions in the brain, lungs,
spleen, adrenal cortex and lymph nodes. There are characteristic virus inclusion bodies at the periphery of
these necrotic lesions in fresh experimental cases but, because of autolysis, they are not always
demonstrable in field cases of abortion. The virus has been found in all fetal tissue and is concentrated in the
cotyledons. Following abortion, the following samples should be submitted for laboratory examination.
Paired serum samples are taken from the dam at the time of abortion and a second set of samples 2–4 weeks
later. However, since cows may have been infected up to 4 months before abortion occurs, a significant rise
in antibody titers is unlikely to be demonstrated. Serological examination of paired serum samples from at
least 10 cows in the herd should reveal seroconversion or a four-fold increase in titers if IBR infection is
active in the herd. For subsequent fluorescent antibody tests, pieces of fetal tissue, particularly kidney and
adrenal gland, should be taken together with a piece of placenta. Such tests that demonstrate specific focal
fluorescence are diagnostic of the disease. Following the presence of genital lesions, vaginal swabs,
preputial washings and semen should be placed in virus transport medium. Paired serum samples should be
taken from the affected cows.
Treatment and control
Spontaneous recovery of the genital lesions will occur and therefore treatment is not really
necessary; however, the administration of emollient creams to the vulva, vagina and penis may be useful.
Vulval stenosis and penile/preputial adhesions and phimosis can occur during the healing phase. Infected
animals should be isolated and natural service suspended. Vaccination is the most effective way of
controlling the disease; a number of live, attenuated vaccines are available, often combined with a bovine
parainfluenza virus vaccine. Heifers should be vaccinated after 6 months of age and before their first
service; thereafter, annual vaccination is preferable. Pregnant animals should only be vaccinated with a
killed vaccine. Both the intranasal and intramuscular routes can be used. Vaccination of bulls is of
questionable value since on they will be seropositive blood testing and may be rejected for sale as being
infected. Routine examination of semen for the presence of the virus is preferable as a method of control.
Other viral causes
Catarrhal vaginocavititis
This contagious, mainly venereally transmitted, disease was first described in South Africa (Van
Rensburg, 1953); since then it has been reported in many countries. It is caused by an enterovirus from the
enteric cytopathic bovine orphan (ECBO) group.
Clinical signs. Affected animals have a profuse, postcoital, non-odorous, yellow, mucoid vulval discharge.
The cervix and vagina are inflamed but there are no pustules, such as occur in IPV infection, and no fever.
The typical yellow gelatinous exudate frequently accumulates in the vagina, varying in quantity from a few
to several hundred millilitres. The disease persists for a few days to a few weeks. Only a few animals show
clinical signs of the disease at any one time. As a consequence, pregnancy rates are reduced and there are
prolonged, irregular returns to oestrus, presumably due to late embryonic death. In some herds, fetal
mummification, abortion and stillbirth have been reported as being a problem. Bulls may or may not become
clinically infected but, in Belgium, Bouters et al. (1964) have provided definite proof of the association of
two ECBO serotypes with seminal vesiculitis and infertility lasting up to 90 days. The penis and prepuce do
not show the lesions that occur following BHV-1 infection.
Diagnosis. The most reliable method of diagnosis is serological examination of paired blood samples,
collected at least 15 days apart, for evidence of rising antibody titres; the first sample should be collected as
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soon as possible after the disease is suspected. The virus can be isolated from vaginal mucus, but the
recovery rate is frequently low (Huck and Lamont, 1979).
Transmission and pathogenesis. Although the disease is transmitted venereally, it can also be spread by
faecal contamination of the vulva, or by animals licking the perineum of infected and noninfected
individuals; hence the disease can occur in virgin heifers.
Treatment and control. There is no specific treatment or vaccine. Infected bulls should not be used for
service for several months, even after clinical signs of disease have disappeared. Potentially infected animals
should be isolated after purchase and, in closed herds, serological examination of potential additions to the
herd might be contemplated.
Transmissible genital fibropapillomas
Wart-like tumors commonly occur on the penis of young bulls, and occasionally similar growths
occur on the vulva, perineum and vestibulovaginal epithelium of heifers. They are caused by a virus of the
papovavirus group and are transmitted by contact with infected animals. These fibropapillomata regress
spontaneously in 2–6 months; the speed of regression may be expedited by the use of a wart vaccine. Except
in so far as the larger tumors (which may be removed surgically) might interfere mechanically with coitus,
they do not cause infertility in female animals.
MYCOTIC ABORTION
CHLAMYDIAL AGENTS: BOVINE CHLAMYDIAL ABORTION
C. psittaci is a pathogen of both the male and female bovine genital tract. In the bull it affects the
testes, epididymides and other accessory glands. It causes orchitis, possibly in association with Mycoplasma
species. However, it particularly affects the vesicular glands, where it is believed to be involved in the
seminal vesculitis syndrome. The organism is sometimes excreted in the semen of affected bulls, although it
has also been isolated from bulls that were clinically normal. Chlamydial infection also affects fertility in the
cow. If contaminated semen is used then, after fertilization has occurred, there will be embryonic death
either due to a direct effect upon the embryo or, more likely, via its effect upon the endometrium. C. psittaci
also causes abortion. Characteristically, abortion occurs at 7–9 months of gestation without any other
clinical signs, although experimental infection is followed by a short period of pyrexia and a leucopenia. The
lesions following abortion are fairly characteristic. The intercotyledonary areas of the placenta are more
frequently affected, being thickened and leathery in appearance with a reddish white opaque discoloration;
edema is quite common. In the aborted fetus, the liver is enlarged with a coarsely nodular surface, firm
consistency and a mottled reddish-yellow color. The organism can be cultured from aborted fetuses and
discharges following the use of transport media. Giemsa-stained smears for the identification of elementary
bodies or inclusions are also useful. Serological tests such as the CFT have been used but are generally too
insensitive. It is likely that the ELISA tests, used to detect the infection in sheep, will be developed for use
in cattle. Tetracycline's could be used to treat pregnant cows that have been exposed to infection. Pregnant
animals should be segregated from potential sources of infection. Vaccines are available for use in sheep but
none has yet been developed for use in cattle. Following abortion there should be a natural immunity.
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