Download Ommon Infectious Conditions

COMMON INFECTIOUS CONDITIONS
The purpose of this section is to review the basics of some of the more common infectious
diseases encountered in the clinic setting. You should have a thorough understanding of
these conditions and be able to effectively communicate this information to clients using
terminology and recommendations that are understandable and realistic for the client.
The vast majority of animals coming in to the clinic have had little or no previous veterinary
care or vaccination history. Many of the animals live outdoors and roam freely, coming in
contact with other domestic and wild animals on a regular basis. The incidence of parasite
infestation and infectious diseases are high. An important part of your role as a veterinary
professional includes educating clients about the prevention of these conditions through good
husbandry, vaccination and veterinary treatment.
CANINE DISEASES
Canine Gastroenteric Viruses
Viral diarrhea needs to be differentiated from diarrhea due to worms, diet or numerous
other possibilities. Usually the wateriness, large amount, bloodiness and bad odor of the feces
coupled with a definitely ill animal points to a viral infection. The enteroviruses are very hardy
and contagious and require meticulous sanitation to prevent transmitting the infection to other
animals. Any animal exhibiting signs of enterovirus infection should be isolated from other
patients and handled with appropriate infection-control precautions.
Canine Parvoviral Enteritis
Agent: Canine Parvovirus (non-enveloped)
Transmission: This highly contagious virus is shed in the feces of infected dogs for several
weeks. Ingestion of infected feces is the most common way animals get the disease. The virus
can remain infective for years in the environment.
Incubation Period: 3 to 8 days.
Effects: Viruses attach to the lining of the small intestine causing bleeding, fluid loss, and
electrolyte loss. The virus also depresses the number of white blood cells. Symptoms are
vomiting, loss of appetite, lethargy, diarrhea (usually bloody), fever and rapid dehydration.
Dogs usually die or quickly recover. All ages can be affected with mortality in 8 to 12 week old
puppies being very high.
Treatment: Treatment of parvo is aimed at minimizing symptoms and supporting the patient
through recovery. Intravenous fluids, antibiotics, antiemetics and anti-diarrheals are all used.
Prevention: Both killed and modified live vaccines are available. The modified live is
recommended as it is best at overcoming maternal antibodies and gives the longest protection.
Feline panleukopenia vaccine can be given to young pups to override maternal antibodies.
Typical vaccination schedule is one injection at weaning and then boosters every 2 to 3 weeks
until pups are 16 to 18 weeks old. Adults are generally given an annual revaccination.
The parvoviruses are extremely hardy and capable of surviving in some conditions for up to a
year. Many standard disinfectants are not effective against parvoviruses. Sodium
hypochlorite (household bleach) at a dilution of 1:32 is the most effective disinfectant.
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Canine Coronaviral Gastroenteritis
Agent: Canine Coronavirus
Transmission: This virus is highly contagious, spread through infected feces. and is shed for 2
weeks by infected animals. Coronaviruses do not persist in the environment like parvo.
Incubation Period: 24 to 36 hours.
Effects: Disease is very similar to parvo, but is milder. Loss of appetite. vomiting, diarrhea, and
depression occur. Feces may contain blood or mucus and often are yellowish. Usually fever is
absent. Dehydration is the major problem. Mortality is not high, but can be fatal in puppies.
Prevention: Killed virus vaccines are available.
Treatment: Fluids and antibiotics as in parvo
Canine Respiratory Viruses
These viruses attack the upper respiratory lining and make conditions suitable for
Bordatella bronchiseptica and other bacteria to grow. This leads to kennel cough, which is
discussed more fully below. Unfortunately, one of these respiratory viruses is canine distemper
Every case of canine upper respiratory disease must be considered a distemper suspect.
Canine Distemper
Transmission: This highly contagious disease spreads primarily through aerosol droplets from
infected animals. Infected dogs may shed the virus for months. The virus does not survive
well in the environment.
Incubation Period: 7 to 14 days
Effects: After inhalation, the virus reproduces and spreads throughout the blood stream
and lymphatic system. The first symptom of this is a fever lasting 1 to 3 days. There is a
concurrent suppression of white blood cells. Thick cloudy discharges come from the eyes and
nose. Depression, loss of appetite, and diarrhea are common. Some dogs develop thickened
skin on the pads and nose ("hard pad").
If the animal survives the initial disease course, nervous system symptoms may develop and
usually do in dogs that exhibit hard pad. These symptoms run from localized twitching in a
muscle group to weakness/paralysis to convulsions/seizures. This may last only 10 days but
usually lasts weeks or months. These symptoms may disappear and then return and are due
to viral effects in the brain and nervous system. Animals may die from this syndrome.
Mortality is often high in unvaccinated animals. Recovered animals may die from future
complications. Old dog encephalitis is a separate nervous system problem that may occur
years after the disease with no interim symptoms.
Treatment: Antibiotics for secondary bacterial infections, fluids for dehydration, and
anticonvulsants and sedatives for nervous manifestations are all useful therapies. Many
animals will not respond or recover.
Prevention: Modified live virus vaccines are available. The ideal course is to vaccinate every
2-3 weeks after weaning until 16 weeks of age. Modified live measles vaccines can be used to
produce immunity in the presence of maternal antibodies.
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Canine Parainfluenza
Transmission: This highly contagious virus spreads through aerosol droplets. It does not
survive long in the environment.
Incubation Period: 5 to 10 days
Effects: The virus attacks the upper respiratory passages and produces mild disease on its
own. More serious disease results from colonization by Bordatella bronchisepeptica or other
bacteria. Watery discharge from the nose and a cough are primary signs. Bacterial invasion
turns discharges thick and cloudy.
Treatment: See Infectious Tracheobronchitis.
Prevention: Modified live virus vaccines are available. Two initial vaccinations are necessary
to provide protection. The second is given 2 to 4 weeks after the first. Puppies receive the first
vaccination at weaning. Annual revaccination is necessary.
Canine adenovirus type 2
Transmission: Aerosol transmission is most common. Short-lived in the environment.
Incubation Period: 5 to 10 days.
Effects: The virus attacks the lining of the upper respiratory system. The severity of the
tracheobronchitis depends on the animal's environment. Poor ventilation increases the
severity of the disease. Bacterial complication is common.
Treatment: See Infectious Tracheobronchitis.
Prevention: Modified live virus vaccines are given on the distemper schedule. One dose
usually gives sufficient protection. Modified live vaccines for CAV - 1 (Infectious Canine
Hepatitis) also protect the animal against CAV -2.
Infectious Canine Hepatitis (Canine adenovirus type 1)
Transmission: This contagious disease is spread through the urine, feces, and saliva of
infected animals. Dogs shed virus in the urine for over 6 months and the virus can survive in
the environment for several weeks or months.
Incubation Period: 4 to 9 days.
Effects: An infected dog first spikes a fever of over 104oF that lasts 1 to 6 days. Tachycardia
and a decrease in the white cell count corresponds to the virus spreading throughout the body
into the liver, spleen, kidneys, and lung. Depression, loss of appetite, watery discharge from
eyes and nose, and eye infections all develop. Some animals show hemorrhages in the mouth
lining, abdominal pain, and vomiting or swelling in the front of the body. Recovery and weight
gain will be slow with a quarter of the affected animals developing corneal edema in both eyes
one week later. Chronic hepatitis may occur. Mortality is high in young dogs.
Treatment: Daily blood transfusions may be necessary. Fluids and antibiotics are used to
treat dehydration and bacterial invasion.
Prevention: Modified live vaccines are available. This vaccine also cross-protects the animal
against CAV-type 2. One or the other is usually combined with the distemper-parvo series.
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Infectious Tracheobronchitis (Kennel Cough)
Agent: Bordatella bronchiseptica
Transmission: This a highly contagious disease complex is spread through aerosolized
particles (coughing and sneezing). Canine adenovirus type 2, canine parainfluenza virus, or
canine distemper generally initiates the disease. B. bronchiseptica follows and colonizes the
damaged area. Separately or simultaneously, other gram-negative bacteria may be involved.
Stress and environmental factors can increase susceptibility.
Incubation Period: 5 to 10 days.
Effects: Harsh dry coughing attacks followed by retching and gagging are typical symptoms.
Gentle palpation of the trachea will elicit coughing. Dogs may become depressed and stop
eating, or may appear otherwise active and normal. Temperature is usually normal.
Bronchopneumonia with fever, heavy nasal discharge, and severe depression may occur in
the young, the stressed, and the elderly. Without complications, the disease is self-limiting
with worst symptoms over after 5 days and all signs of the disease gone in 10 to 20 days.
Stress may cause a relapse during recovery. Mortality is low unless there are complications.
Prevention: Modified live intra-nasal and killed bacterin injectable vaccines are available. The
intra-nasal is recommended as it produces faster immunity and gives better local immunity in
the respiratory passages. The bacterin immunity lasts longer, but is not concentrated in the
respiratory passages. There are also local skin reactions produced in some dogs from the
bacterin. Vaccine is best if given twice a year to dogs likely to be exposed.
Treatment: Cough suppressants control coughing spasms and break the cough cycle.
Antibiotics are generally only effective if delivered to the by inhalant administration.
Leptospirosis (Canine typhus, Infectious jaundice)
Agent: L canicola
Transmission: Disease is spread by infected urine contacting mucous membranes. Less
commonly it is spread through the contaminated food or water. The bacteria localizes in
kidneys and can be shed in urine for months or years. It is often waterborne and survives
extended periods in water. Dogs of all ages are affected with a much greater incidence in
males. The disease is zoonotic.
Incubation Period: 5 to 15 days.
Effects: In severe cases, there is a sudden onset with weakness, food refusal, vomiting, fever
of 103° to 105 °F and mild eye infection. After a few days, the temperature drops and the dog
becomes depressed with difficulty breathing and severe thirst. Jaundice may appear as a first
symptom or later. Abdominal pain, bloody urine, and urine casts result from kidney infection.
Bloody vomiting and diarrhea are common. Chronic kidney disease and infection can result.
Mortality is rarely over 10 percent.
Prevention: Bacterin vaccines are available that protect against most serotypes. They are
usually given in combination with distemper-parvo vaccination.
Treatment: Tetracycline and streptomycin are useful in acute infections. Large doses of
dihydrostreptomycin can be used to terminate the carrier state. The rest of the treatments are
symptomatic, such as giving fluids for the dehydration and treating metabolic acidosis.
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FELINE DISEASES
Feline Upper Respiratory Disease Complex
The viruses under this heading along with the Chlarmdia psiitaci cause far and away
the majority of upper respiratory disease in cats. Although general symptoms are slightly
different, in any individual animal it is not possible to say which disease is present on the basis
of clinical symptoms alone. Of importance is the fact that all 3 of these major respiratory
pathogens can develop carrier states and chronic infections. Healthy looking animals may be
constantly shedding virus and/or relapsing when subjected to stress.
Feline Viral Rhinotracheitis (Feline herpes virus)
Transmission: This highly contagious virus is shed from oral and nasal secretions. It causes
40 to 45 percent of feline URI. Aerosol droplets from sneezing and indirect contamination
through objects and caretakers are the major routes of infections. The virus is shed
intermittently and stress may cause a relapse. The virus does not last long in the environment.
Incubation Period: 2 to 6 days.
Effects: Fever, frequent sneezing, eye infections, infection of nasal passages, and salivation
are typical symptoms. Discharges from eyes and nose are clear and watery to start, but
become thick and cloudy. Depression and loss of appetite develop. Ulcers of the cornea and
mouth may develop with all affected areas being susceptible to secondary bacterial infection.
Signs last 5 to 10 days in mild cases and up to 6 weeks in severe cases. Mortality is low with
more deaths in kittens and elderly cats.
Treatment:: Support animal with symptomatic therapy. Antibiotics are used in cases of
secondary infection. Assist feeding and fluids may be necessary. Idoxuridine (topical antiviral) eye drops may inhibit the disease if given when very first signs appear.
Prevention: Modified live injectable vaccines are available. Vaccinate kittens at weaning and
every 3 to 4 weeks until 12 weeks old. Annual revaccination is recommended. Modified live
intranasal vaccines give faster response, but may generate sneezing 4 to 7 days postvaccination.
Feline Calicivirus
Transmission: This highly contagious virus also accounts for 40 to 45 % of all feline upper
respiratory infections. Virus is shed continuously by infected cats and spread via aerosol
droplets and contaminated objects.
Incubation Period: 2 to 6 days. Average is shorter than FVR.
Effects: Fever, lack of appetite, and depression are common. Virus preferentially attacks the
tissues of the mouth and lungs. Some strains cause salivation and ulcers on the tongue,
nostrils and hard palate while others produce pneumonia and fluid collection in the lungs. The
superficial lesions heal rapidly and the cat will eat again 2 to 3 days after the beginning of
symptoms. The disease usually lasts 7 to 10 days. Mortality is higher than in FVR and may
reach 30% of those affected.
Treatment: Symptomatic as for FVR except that idoxuridine is ineffective against calicivirus.
Prevention: Vaccination with modified live virus vaccines is typical. This vaccine is usually
included with injectable FVR vaccine.
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Feline Pneumonitis (Chlamydia psittaci)
Transmission: The disease spreads through aerosol droplets and contaminated objects. C.
psittaci accounts for 5 to 10 percent of infectious feline respiratory disease and may be a part
of that disease complex. The agent is zoonotic, but is rarely transmitted from cats to human.
Incubation Period: 5 to 10 days.
Effects: The external eye is the major area infected. Copious tears and occasional sneezing
are typical signs. A fever may develop when ocular discharges turn thick and cloudy.
Recovering animals may relapse, and disease may become chronic. Mortality is low.
Treatment: Tetracycline is considered the most effective broad-spectrum antibiotic for this
disease. Eye drops and symptomatic therapy may be necessary.
Prevention: Cats older than 12 weeks old receive one dose to start. Kittens vaccinated earlier
than that require a second dose at 16 weeks of age. All animals are revaccinated annually.
Feline Panleukopenia (Feline distemper, Feline infectious enteritis)
Agent: Feline parvovirus
Transmission: This disease is highly contagious. All secretions and excretions of infected
animals are loaded with virus. These are transmitted directly or through contaminated objects.
The virus can survive years in the environment.
Incubation Period: 3 to 7 days
Effects: Fever with depression, appetite loss and weakness occurs first. Diarrhea and vomiting
may occur one or 2 days after onset. White blood cell numbers are severely depressed leaving
the animal open to infection. Dehydration is severe. The disease course is usually 5 to 7 days.
Infections of pregnant cats or newborn kittens can results in damage to the cerebellum and
related problems with coordination and mobility. Mortality is very high and can reach 60 to 90%
in kittens.
Prevention: Both modified live and killed virus vaccines are available. Modified live vaccine is
recommended for its higher titers and better ability to overcome maternal antibodies.
Vaccinate the kittens at 8 to 10 weeks and then every 3 to 4 weeks until 12 weeks old.
Revaccinate annually.
Treatment: Fluids, nutrients, and antibiotics treat the disease symptomatically. Blood
transfusions can help by replacing white blood cells.
Feline Leukemia Virus
Agent: Feline leukemia virus
Transmission: This disease is moderately contagious and spread primarily through cat to cat
contact. Saliva and blood are infective. Repeated exposure often is necessary to transmit the
disease. Virus does not survive long in external environment. No evidence exists of this virus
causing human disease.
Effects: 70 to 80% of all cats infected will develop some type of immunity and be unaffected by
the virus. Some of these will be chronic shedders of virus, however. Of those that develop
disease, the most common effect is severe depression of the immune system. This means that
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the cat will die of some other disease it is unable to combat. A small percentage will develop
leukemia or other cancers. Depression, anemia, and loss of appetite are common signs. 90 to
95% of all chronically diseased cats will be persistently infected by feline leukemia virus.
Mortality in cats showing disease is 100%. Kittens born to infected mothers usually die within 2
weeks.
Prevention: Killed virus vaccine is available. Doses are given at 9 to 10 weeks of age, 3 to 4
weeks later, and then 3 to 4 months after that. All ages will require the series of three with
protection appearing after the last dose. Annual revaccination is necessary.
Treatment: Symptomatic for chronic disease problems with specific treatment being given for
each secondary disease. No permanent recovery is possible at this time.
Feline Infectious Peritonitis
Agent: Feline coronavirus
Transmission: This contagious disease is spread through contact with urine and blood from
infected cuts. Most affected animals are between 6 months and 2 years of age. Virus does not
survive well in environment.
Incubation Period: Weeks to months.
Effects: The original infection usually has no symptoms. The disease will have a very slow
onset with a low-grade non-responsive fever leading into depression, loss of appetite, a
excessive number of white blood cells, and a higher fever. Cat will become comatose with a
sub-normal temperature.
The most common form of the disease, the dry form, produces adhesions between organs in
the chest and/or abdomen. The wet form produces large amounts of yellowish fluid and
distension in these same areas. Mortality is extremely close to 100%;
Treatment: The entire aim is to make the cat comfortable as all therapy is generally ineffective.
INTERNAL PARASITES
Coccidia
Agents: Isospora species are most common.
Lifecycle: These are single cell protozoans. They produce oocysts (these are egg-like) through
sexual reproduction to be passed in the feces of infected animals. These require a few days of
proper environmental conditions to become infective. These are either directly ingested by the
next cat or dog or go into the muscle of a rodent or other intermediate host. A cat or dog may
also be infected through eating the intermediate host.
Effects: Diarrhea (sometimes bloody), weight loss, and dehydration are typical. These result
from the coccidia reproducing and attacking the intestinal lining. Puppies and kittens under 1
month old are the most commonly affected. Stress and other diseases can precipitate this
disease.
Prevention: Removal of feces before oocysts become infective is important.
Treatment: Trimethoprim with sulfas is good for clinical cases. Fluids and electrolytes are
symptomatic therapy.
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Roundworms
Agents: Taxocara canis T. cati Taxascaris leonina
Life cycle: Puppies are usually infected with T. canis before birth through the migration of larva
from maternal tissues. Direct transmission requires swallowing the infective egg. Larva migrate
to liver and lungs, are coughed up and swallowed, and mature in the small intestine. In older
animals, the larva migrate to and become dormant in muscle and other tissue. T. Ieonina is
acquired through eating an egg or larva encysted in an intermediate host.
Effects: Young animals will grow slowly, have a poor hair coat, and be "pot bellied." Diarrhea
may be present and worms can pass in feces or vomit. Migration can damage the lungs and
lead to pneumonia.
Treatment: Pyrantel pamoate is the drug of choice in young puppies.
Hookworms
Agents: Ancylostoma caninum A. rubaeformis A braziliense
Life cycle: Hookworms are usually transmitted to the young through mother's milk or through
eating larva. Larva can also invade directly through the skin. Prenatal infection is not common.
Skin invaders migrate to the lungs, are coughed up and swallowed, and develop in the small
intestine. In older animals, larva migrate to muscle and become dormant.
Effects: Hookworms are blood feeders that remove a plus of tissue from the intestinal wall.
Rapid blood loss occurs. Diarrhea with dark tarry feces is typical. Anemia, weakness, and
chronic wasting may develop. This predisposes the animal to further viral or bacterial disease.
Treatment: Pyrantel pamoate is the drug of choice. Blood transfusions may be necessary. A
high protein diet aids recovery.
Canine Whipworms
Agent: Trichuris vulpis
Lifecycle: Eggs become infective 2 to 4 weeks after production, and may remain viable for
years. Drying will destroy them. Eating infective eggs is the only method of transmission. Larva
develop in the small intestine and the adults live in the cecum.
Effects: Weight loss and diarrhea (with fresh blood) are major signs. Anemia may develop.
Treatment: Mebendazole, and pyrantel are effective. Ivermectin is unapproved but effective.
Tapeworms
Agents: Dipylidium caninum (90%) Taenia taeniae/jbrmis
Lifecycle: Eggs are passed separately or in segments and eaten by a flea, mouse, or other
animal. Eating the intermediate host is the only way a dog or cat becomes infected. Flea-borne
Dipylidium accounts for most infestations in dogs and cats.
Effects: Serious disease is rare. Mild diarrhea and unthrifty appearance are typical signs.
Prevention: Effective flea control and preventing ingestion of rodents is the best preventative.
Treatment: Praziquantel is drug of choice.
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Heartworm
Agent: Dirofilaria immitis
Lifecycle: Microfilaria are released into the infected animals' blood stream by adult female
worms. Mosquitoes ingest the larva. Over a 2 week period the larva becomes infective and
migrates to the insects' mouth parts. It enters the dog during the next feeding of a mosquito. It
develops in the area it enters for a couple of months then migrates to the right ventricle of the
heart by 2-4 months post-infection. The worm then takes 2-3 months to reach maturity and
produce offspring.
Effects: Exercise intolerance, coughing, gasping for breath, and slow chronic weight loss are
all signs of heartworm disease. Heart and lung problems result from obstruction of blood flow
by the bodies of the living and dead worms.
Prevention: Diethyl carbamazine given daily and ivermectin given monthly are the only two
approved preventatives. Puppies can be stared on preventative without prior testing. But
animals over 4 months of age should be heartworm tested before preventative is given.
Treatment: Arsenamide kills the adults slowly, while concurrent steroids, antibiotics, and
aspirin help prevent complications. In severe cases, surgical removal may be necessary.
EXTERNAL PARASITES
Fleas
Agents: Ctenocephalides felis, C. canis
Life cycle: Fleas feed on a host, mate, and then the females lay hundreds of eggs which drop
off and pupate. Adult fleas emerge from the cocoons to restart the cycle. The entire lifecycle
takes 3 weeks in a favorable environment. Fleas can go 2 months without feeding, and can
reproduce explosively. Fleas also transmit Dipylidium canimun, the tapeworm.
Effects: Repeated itching is the first sign of a flea problem. Heavy infestations may result in
anemia from the amount of blood eaten. The most serious result is when animals develop
allergic reactions to flea saliva and self-mutilate their skin due to the intense itching.
Treatment: Applying a suitable insecticide to both the animal and the environment is the
most common control method. Many different types are available.
Ticks
Agents: Dermacentor sp. Rhipicephalus
Life cycle: Ticks are blood feeders. After mating, the adult females engorge from feeding and
drop off to lay their eggs in the environment. The small six-legged seed ticks attach to a host,
feed, grow, and drop off to molt. They repeat this 1 to 3 times depending on the tick species.
They then are adult and breed. The life cycle can be completed in a couple of months.
Effects: Anemia from the feeding of many ticks is possible. Tick paralysis can result from an
animal's reaction to a feeding tick. Ticks also transmit ricketsial diseases. The ear canal and
shoulders are typical sites of feeding. Ticks should be removed with a forceps to prevent
breaking off the mouth parts in the skin and causing infection.
Treatment: Both the environment and animal must be treated to achieve effective control.
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Sarcoptic Mange
Agents: Sarcoptes scabei cards Natoedres caii
Life cycle: These highly contagious mites spread through direct contact. Eggs are laid in skin
tunnels as the female burrows. The entire life cycle of 17 to 21 days is spent on the host.
Incubation Period: 2 to 8 weeks.
Effects: Intense itching with self-mutilation and secondary bacterial infection is common. Dry.
thick, wrinkled areas with possible crusts on the head, under the chest, and around the tail
head. If untreated, animals become debilitated and may die.
Treatment: Lime sulfur dips, rotenone, and amitraz have all been used. In the clinic setting,
the typical treatment (for all but collie-breeds) is ivermectin. Two or more treatments may be
necessary.
Demodectic Mange
Agents: Demodex canis D. cati
Life cycle: The mite lives in hair follicles and is found on many healthy animals. Direct contact
transfers wandering mites to a susceptible host, usually received when nursing from the dam.
There is a hereditary predisposition to developing demodectic mange, and other
immunosuppressing factors play a role. The disease is not very contagious. The life cycle of
egg to mite requires 20 to 35 days.
Effects: The localized form is most common with small, discrete areas of hair loss on face and
front legs. About 90 percent of these cases resolve spontaneously. When animals develop
generalized demodecosis. the skin becomes reddened, oozes serum, and is complicated by
bacterial infection. These may be very difficult to cure as there often is an underlying problem.
Treatment: Amitraz is considered drug of choice for generalized infection and is repeated until
mites are absent after 2 consecutive treatments.
Earmites
Agent: Otodectes cynotis
Life styles: Contact with infested individuals transmits mites. Cat to dog and vice versa spread
is common. The adults live in the ear canal and pierce the skin to suck lymph fluid. Eggs are
laid there and the life cycle repeats every 2 weeks.
Effects: Irritation and crusts appear in the ears. The animal shakes its head, scratches its ears,
and can self-inflict wounds. Secondary bacterial infections and abscesses are common in the
ears and wounds.
Treatment: Topical oils and/or insecticides are applied to the ear canal. Treatment is repeated
and continued for 7 to 9 days to break the life cycle. Ivermectin administered topically once is
also effective (may need to repeat in 2 weeks).
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OTHER CONDITIONS
Ringworm (External Fungal Infection)
Agents: Dogs — Microsparum canis, M. gypseum, Trichophytan meraagrophaes
Transmission: Most cases appear after contact with infected animals, contaminated objects,
or contacting soil-borne organisms. Contact only sometimes results in infection. Young, old,
and immune-compromised individuals are most susceptible. The disease is not that
contagious.
Effects: These organisms generally only grow in dead tissue. This confines them to infesting
hair and upper skin layers. Kittens show spots of hair loss with scaling and crusting around
the face and ears. Itching may be absent. Dogs show circular spots with broken hair
protruding through crusts. Half of all M. canis strains will fluoresce under a black light.
Prevention: Topical treatment (miconazole, chlorhexidine etc) applied to lesions will help
prevent spread to others animals.
Treatment: Disease is usually self-limiting. Prevention of spread to others is important.
Griseofulvin can be used for severe cases.
Rabies
Agent: A rhabdovirus
Transmission: The virus is usually spread by a bite-introducing infected saliva into the wound.
Rarely, transmission is through contamination of a pre-existing wound with the virus.
Incubation Period: Usually 15 to 50 days.
Effects: The virus will slowly work its way from the wound along nerves to the brain and
salivary glands. A change in any behavior may be a sign of rabies. The body temperature is
unchanged and the animal will usually stop eating and drinking and go off alone. Often there
is stimulation or irritation of the urogenital system.
After this first stage, animals may go into either of two syndromes. In the paralytic or "dumb"
form, an inability to swallow progresses to paralysis of the entire body and death soon after.
The furious form of the disease is characterized by irrationality, aggression, and loss of fear.
Convulsions and eventual paralysis lead to death. Dogs rarely live beyond 10 days after onset
of signs. Cats generally develop the furious form, while the majority of dogs display the
paralytic form.
Every animal bite is a rabies possibility. Rabies in the early stages can masquerade as any
other disease. Mortality is 100 percent in domestic animals and humans.
Prevention: Killed virus vaccines are given every 1 to 3 years. The first vaccination is given at
4 to 6 months of age. Both dog and cats should be vaccinated. State requirements often
specify the age of initial vaccination, type of vaccine needed, and route of administration.
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Rickettsial Disease
Rickettsia are bacteria that are unable to synthesize certain proteins and enzymes on
their own. They must have these supplied by a host cell and are therefore obligate
intracellular parasites.
Agents: Ehrlichia canis, Ridcatsia ridcaaii (Rocky Mountain Spotted Fever).
Transmission: These are tick-borne diseases. Ticks carry the rickettsia for months after
feeding on an infected dog. Blood transfusions from infected animals are also implicated.
Rocky Mountain Spotted Fever is zoonotic and generally shows no symptoms in dogs.
Incubation Period: 2 to 3 days.
Effects: These agents infect the cells of the blood stream. Fever, depression, and loss of
appetite are common. Bleeding disorders and chronic wasting occurs in the worst cases.
Mortality is rare in acute cases, but more common in the chronic cases.
Prevention: Effective tick control will help prevent disease. Tetracycline can be fed as a daily
preventative.
Treatment: Tetracycline is the antibiotic of choice against this disease. Blood transfusions and
supportive therapy may be necessary.
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