Download Neosporosis

JULY 2016 - NEWSLETTER
Neosporosis
Neosporosis is caused by the protozoan parasite Neospora caninum and the
most commonly identified cause of infectious abortion in the UK. Infection in
the average UK dairy herd is estimated to cost in the region of £3000 per year.
Cattle become infected by one of two routes. Firstly from the
ingestion of oocysts (parasite eggs) in the faeces of infected
dogs through contaminated feed or water. The parasite then
goes through a stage of multiplication in the cow’s bloodstream
before infecting cells and forming tissue cysts. The dog becomes
infected by eating tissue containing these tissue cysts such as
placenta, aborted foetus or meat.
“
Secondly cattle can become infected during pregnancy.
Calves from infected dams have a 80-90% chance of
being born infected. This is thought to be the most
common mode of transmission of the disease. There is
currently no evidence of adult cow to cow transmission.
The most common way of introducing Neospora onto a farm is
thought to be buying infected cattle, but infection can also be
brought on by dogs.
After infection, a dog will shed for only 2-3 weeks but does not usually show any clinical
signs. After this period the dog develops immunity and is no longer a threat to cattle.
Currently there is no evidence that foxes or any wildlife in the
UK have a role in spreading bovine neosporosis, however this is
an area of ongoing investigation.
Not all cows infected with Neospora will abort but, they are
5 to 7 times more likely to abort than uninfected animals.
The outcome of Neospora infection depends on what stage of
pregnancy infection of the foetus occurs. In early pregnancy it
generally leads to foetal death, in mid-pregnancy infection can
cause foetal death or the birth of infected calves sometimes
with neurological problems, generally in late pregnancy calves
are born infected but otherwise normal. Abortions to Neospora
tend to occur around 5-7 months pregnancy. Cases of early
foetal death result in reabsorption of the embryo and return
to oestrous.
”
Diagnosis of Neospora in an abortion is made at post-mortem
of the foetus, blood sampling is the only method of diagnosis in
the live animal. Though positive blood test in the dam doesn’t
confirm Neospora as the cause of abortion only that she is
infected. Screening the herd for Neospora can be difficult as
antibody levels fluctuate, negative results doesn’t always mean
an animal is not infected. Screen cows in mid to late pregnancy
gives the best chance of revealing infected animals, such as
at drying off.
Biosecurity is essential to prevent Neospora being brought into
your herd, sourcing cattle from herds tested free and testing
animals after arrival is essential.
Cows id
entified
as
infected
should b
bred to
e
beef to
prevent
the dise
ase est
Currently there are no vaccines or treatments for Neospora, control is based around biosecurity, testing and in future g ablishing
eneratio
ns
breeding management. Dogs should be kept away from calving areas and afterbirth, and foetal material
or culle
d.
disposed of quickly. Rodents may act as intermediate hosts passing infection from infected foetal material
to the dogs and so robust rodent control is important. Cows identified as infected should be bred to beef to
prevent the disease establishing in future generations or culled. After identifying infected animals the dam and any daughter
should be tested to establish the extent of infection in that family line.
Hypocalcaemia
Many herds have now turned cows out to grass, however if not managed well, a poor transition back to milking can lead to high
levels of disease in freshly calved cows. Incidence of both clinical and sub-clinical hypocalcaemia can often increase as dry and
calving cows are turned out to grass. Often this is restricted purely to a sub-clinical level meaning we don’t see any clinical effects
of the low calcium level. Sub-clinical hypocalcaemia if often a gateway disease for other conditions:
• 8 times more likely to get mastitis
• 3 times more likely to suffer from difficult calvings
• Twice as likely to have retained placenta or displaced abomasum
• 12 days longer calving to conception
• Lower conception rates
Periodically testing freshly calved cows calcium levels is important to monitor the prevalence of hypocalcaemia on your farm and
assess the need for dietary change or calcium therapy around calving to reduce risk. Any increase in peri-paturient disease should
also raise alarm bells to problems with transition cow management and diet.
BVD & IBR
We recently screened all Oakhill dairy herds for BVD and IBR as part of our monitoring program. 51% of herds were both BVD
and IBR vaccinated, of the BVD non-vaccinated herds, 87% were antibody positive, showing exposure to virus and potential for
infection to be present in the herd. 11% of the non-vaccinated herds had a positive PCR positive result on the bulk tank indicating
active infection and virus circulating in the milking herd. Of the non-vaccinating IBR herds 70% showed exposure to IBR, given IBR
infection is lifelong the virus is therefore present in these herds. The results show the importance of monitoring disease status on
the farm particularly non-vaccinated herds as exposure to viruses is very common. Bulk tank screening is the easiest way to get an
overall view of herd status and indicate if further testing is necessary.
Of the non-vaccinated herds
87%
were
antibody
positive.
Of the non-vaccinated herds
11%
PCR
Positive
Result
01772 861300
www.redrosedairydiscussiongroup.co.uk