Farm Animal Medicine and Surgery. Graham R Duncanson

organisms involved in this disease are multiple but the most important are Eimeria eznernii, E. bovis and E. alabamensis. Tenesmus and diarrhoea, often containing fresh blood, are seen at about a month of age. Diagnosis is by counting oocysts in the faeces using a McMaster slide. Treatment should be rehydration and a coccidiostat, e.g. toltrazuril or diclazuril, orally. Decoquinate or monensin can be used in feed prophylactically (the latter is not licensed in the UK).

       Cryptosporidium parvum

      This organism is not restricted to calves and can cause diarrhoea in other species, including man. It causes diarrhoea in 2-3 week old calves. Diagnosis is from faecal smears stained with Giemsa. Treatment should be rehydration and oral halofuginone lactate.

      Enteric diseases caused by parasites

       Fasciolisis

      In the UK, this condition is caused by Fasciola hepatica (the liver fluke). F. gigantica is found in Africa and Asia. The intermediate host in the UK is Lymnaea truncatula (the water snail). The normal form of the disease in cattle is chronic, with most of the flukes shed within 6 months, leaving the bile ducts irreparably thickened and even calcified. The principal signs are weight loss and diarrhoea, with raised liver enzymes. Diagnosis can be confirmed on a blood test with an ELISA. Eggs may be seen in the faeces and these are diagnostic but often, even in bad cases, eggs are not found. Treatment is with oral triclabendazole which kills adults and immature stages, clorsulon both by injection and as a pour on, and albendazole which only kills the adults.

       Parasitic gastroenteritis (PGE)

      The main parasitic nematodes causing PGE that are found in the UK are Ostertagia ostertagia, Cooperia onocophora, Nematodirus helvetianus, Trichostrongylus axei and Haemonchus placei, there are many other such species found throughout the world. These nematodes do not have an intermediate host and each tends to have different clinical manifestations.

      O. ostertagia manifests as two separate clinical conditions, type 1 and type 2:

      • Type 1 is the more standard form of PGE, with susceptible animals ingesting larvae later on in the grazing season. These become adults in the abomasum in the late summer, causing diarrhoea and ill thrift. High faecal egg counts (FECs) will be recorded. Anthelmintic treatment, unless there are resistant strains, will normally alleviate the problem.

      • Type 2 follows type 1 in that larvae are ingested, but these do not become adults; rather they encyst in the mucosa of the abomasum in large numbers. The encysted larvae lie dormant until a trigger factor in the winter makes them all emerge together, when the animal will not only have severe diarrhoea but will be very ill and may even die. FECs will not be raised but diagnosis can be confirmed by a blood sample to measure serum pepsinogen. Treatment not only consists of anthelmintics but also of dexamethazone and antibiotics to try to reduce inflammation in the abomasal mucosa.

      C. onocophora causes a standard form of PGE like O. ostertagia type 1, but normally slightly earlier i.e. halfway through July in the UK. N. helvetianus is the most common species in cattle worldwide. The eggs, which are very resistant to degradation, will accumulate on pastures for many months and infect calves in the next season. Severe signs of diarrhoea may occur before large numbers of easily recognized eggs (they are twice the size of those of other nematode species) occur in the faeces. T. axei is the very common small stomach worm which causes standard parasitic gastroenteritis worldwide. H. placei does not occur in the UK, but causes severe disease in tropical and subtropical countries. The disease and the diarrhoea may be so acute that the FEC will not have had time to rise to the massive levels seen later in the disease. Prompt treatment with anthelmintics is vital to prevent death.

      Enteric diseases of unknown cause

       Abomasal ulcers

      These are seen in calves and the signs are colic, diarrhoea and melena – which manifests as black faeces. Treatment is symptomatic with a guarded prognosis.

       Jejunal haemorrhagic syndrome

      This is a sudden onset sporadic disease manifest by acute abdominal pain. There is rapid progression to shock, recumbency and death. A possible cause is Cl. perfringens type A. Treatment is symptomatic and rarely successful.

       Vagal indigestion

      This condition of cows used to be called ‘well stomach’ because when the rumen is auscultated the clinician hears a noise like a stone being dropped into a well. The rumen is atonic, perhaps because the vagus is damaged by an abscess in the mediastinum. Treatment is with oral rumen stimulants which offer doubtful efficacy and therefore the prognosis is poor.

      Miscellaneous enteric conditions

       Cleft palate

      This congenital condition, which is usually bilateral, may be inherited. The clinician will be alerted to the condition by milk coming down the nose when the calf sucks. Diagnosis can be confirmed visually and euthanasia should be carried out.

       Congenital erythropoietic porphyria

      This is commonly called ‘pink tooth’ and occurs worldwide. It is an inherited disease related to a simple autosomal recessive gene. The teeth fluoresce in ultraviolet light. Vesicles and necrosis occur in unpigmented areas of the nose and mouth. There is no treatment and animals should be culled.

      Pathogenic causes of diarrhoea in cattle

      These can be classified by pathogen, age of affected animal or another incidence pointer, as shown below in Table 3.1.

Table 3.1. Infectious causes of diarrhoea in cattle.

Pathogen	Age group	Incidence pointer
Bovine viral diarrhoea	Adults	Abortion and linked to mucosal disease (see below)
Campylobacter jejuni and C. coli	Calves	Neonatal
Candida albicans	Calves	After prolonged antibiotic treatment
Coronavirus	Calves and adults	In adults, mainly in dairy cows in winter. Calves aged 3–21 days
Coccidiosis	Calves	4–6 weeks of age
Cryptosporidiosis	Calves	2–3 weeks of age
Enterotoxaemia	Calves	Neonatal, strains with K99 antigen are more pathogenic, may be peracute
Enterotoxaemia	Growing cattle	Clostridium perfringens type D, violent scouring
Fascioliasis	Yearlings and adults	Скачать книгу В начало < 14 15 16 17 18 19 20 21 22 23 > В конец