affects the cow when 8-16 weeks pregnant. The abnormalities seen are limb contracture, brain abnormalities and a twisted neck (see Plate 3). These may result in the need for an embryotomy or a Caesarean section. Cows after parturition do not appear to be shedding virus.
Ureaplasma diversum
This mycoplasma is found in healthy animals and so its role in causing abortion is unclear. It is certainly transmitted venereally, but it is likely that it requires another agent to cause an abortion.
Wesselsbron disease
This viral disease, found in Africa, is caused by an arthropod-borne (mainly Aedes spp. mosquitoes) Flavivirus (Wesselsbron virus) which causes abortion and a fatal disease in neonatal calves. It is zoonotic and difficult to differentiate from RVF.
Endometritis
This condition is seen commonly post calving, particularly if there has been fetal membrane retention. The normal causal organisms are Arcanobacterium pyogenes, Streptococcus spp. and E. coli. In the acute form, the cow will be ill, show pyrexia, have swollen hocks and a bloody smelly vulval discharge. Treatment would be penicillin parenterally and NSAIDs. In the chronic form, the cow will appear normal except for a purulent smelly vulval discharge. Treatment should be aimed at bringing the cow into oestrus with a prostaglandin injection. Uterine washouts were recommended historically but show poor evidence of efficacy.
Mastitis
Mastitis can be attributed to contagious or environmental pathogens or, in the case of summer mastitis, to the fly Hydrotaea irritans.
Contagious pathogens
• These are Staphylococcus aureus, Streptococcus dysgalactiae, S. agalactiae, Corynebacterium bovis, coagulase-negative Staphylococcus spp. (these often colonize the teat canal and are opportunist pathogens), Mycoplasma bovis, M. californicum and Mycoplasma spp.
• They cause inflammation and pain in the udder, as well pyrexia and painful and swollen hocks.
• A milk sample should be taken for culture and sensitivity before treatment is started and then this treatment can be modified when the results are known.
• Although short milk withhold periods are important in dairy cows, effective antibiotic treatment is more important in the long term, not only for the affected cow but also for the rest of the group -bearing in mind that these pathogens are contagious.
• It is important to use the same antibiotic administered into the mammary gland as is used parenterally.
• Mycoplasma spp. present in the udder are not controlled by antibiotics.
• NSAIDs are useful in treatment.
• Dexamethazone should be used with care, making sure that the cow is not pregnant and the organism is being controlled by the antibiotic.
• There is a vaccine available against S. aureus.
Environmental pathogens
• These are E. coli, Klebsiella pneumoniae, Streptococcus uberis, Pseudomonas aeruginosa, Bacillus cereus, Pasteurella spp., Candida spp. and Aspergillus spp.
• E. coli and K. pneumoniae are both very serious pathogens which normally infect newly calved cows. They both produce toxins which cause a peracute disease called ‘toxic mastitis’.
• Toxic mastitis is a specific disease syndrome often causing acute toxicity before mastitis is seen in the udder, and culture of the milk may often be unrewarding.
• Only 30% of affected animals are likely to survive toxic mastitis.
• Treatment of mastitis caused by environmental pathogens should involve NSAIDs and fluid therapy. Antibiotics suitable for use against Gram-negative bacteria are normally given parenterally and into the udder but many authorities consider that this is hardly worthwhile as the organisms have produced the lethal toxins and been destroyed.
• There are many ideas put forward for fluid therapy. The author favours giving large volumes of electrolytes with an Agger’s pump.
• Prevention measures include dry cow therapy, teat sealants and vaccination against E. coli.
Summer mastitis
• This occurs in dry cows and in-calf heifers but rarely in maiden heifers.
• The author has on rare occasions seen it in the mammary tissue of bulls.
• The disease, which is bacterial, is spread by the fly Hydrotaea irritans, which has a predilection for trees.
• There is a sequence of events; initially the udder is colonized by S. dysgalactiae, there is a slight swelling and the animal will be only slightly ill with a pyrexia. If treatment with antibiotics, normally penicillin, is initiated immediately, the disease will not progress further and the infected quarter will be saved.
• If the animal is not treated, other bacteria, namely Arcanobacterium pyogenes, Peptococcus indolicus, Bacteroides melaninogenicus and Fusobacterium necrophorum will colonize and the animal will become ill and the quarter will be lost, even with antibiotic treatment.
• At this stage, the udder discharge will be creamy and malodorous, alerting the clinician to the poor prognosis for the udder.
• Animals will be stiff behind and often their hocks will swell so treatment with NSAIDs as well as antibiotics would be appropriate.
• Prevention is with dry cow therapy, teat sealants and fly control.
Mummified fetus
The aetiology of this condition is obscure; in fact, there may be two conditions with different causes. The most common manifestation is the cow which has been diagnosed as in calf but never develops normal udder enlargement, i.e. does not ‘bag up’ for calving at the expected date. Rectal examination of the uterus will reveal an enlargement but no cotyledons or fremitus. Only if clinicians are certain of service dates, and are 100% certain that there has been no subsequent unrecorded service, should prostaglandin injections followed by dexamethazone be given. These mummified chocolate non-malodorous fetuses of about the size of a hare are difficult to abort. After the abortion, the cow should be served at the first oestrus as this has been shown to be the most fertile. The second much more unusual manifestation -after a prolonged pregnancy – is felt on rectal examination as a bag of bones either in the uterus or actually in the vagina. This small calf is mummified but also purulent and malodorous. The calves can be pulled out of the vagina or are easily aborted with a prostaglandin injection. It is possible that the second scenario is just a sequel of the first scenario which has been invaded by pus-forming bacteria.
Pyometritis
