Farm Animal Medicine and Surgery. Graham R Duncanson
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being normal. Careful lung auscultation should reveal a lack of sounds in the normal animal. Subcutaneous oedema, which is abnormal, will be seen below the mandibles, on the brisket and in front of the udder. The mucous membranes can be checked in the vulva of females or in the conjunctiva of both sexes. The eyes should be checked for abnormalities and any ocular discharge. The mouth should be checked for excess saliva and for abnormal lesions on the mucosa of the lips and tongue. Auscultation of the rumen should reveal contractions every 20 or 30 s. A resonant ping on auscultation of the left flank is abnormal, as is a splashing on simultaneous ballottement and auscultation of the right flank. The consistency of the faeces can be checked on rectal examination.
The history taken should include the type of animal and its age. Knowledge of the number in the group, together with the total number on the farm, is also important. It is useful to find out how long this group of cattle have been on the farm and whether their management has changed recently. Obviously, the number affected by the condition under examination and any deaths that have occurred should be recorded as well. Asking for any other observations is useful. Farmer’s ideas should not be disregarded.
Diseases of the Gastroenteric System
The predominant signs
• Diarrhoea
• Anorexia
• Pyrexia
• Vomiting
• Dysentery
• Tenesmus
• Excess salivation
• Lack of rumination
Diagnosis
The age of the animal, with a full history (including any alteration to diet), should be linked with any abnormal clinical signs to aid diagnosis. An adequate faeces sample – 70 g is recommended – should be taken as rectal swabs are not normally sufficient even for bacteriology.
Causes of enteric disease
• Viruses
• Bacteria
• Protozoa
• Endoparasites
• Poisoning
• Change of nutrition
• Miscellaneous (and unknown) factors
Enteric diseases caused by viruses and their treatment
Bluetongue disease
The causative organism, Bluetongue virus (BTV), is an Orbivirus with 24 serotypes, which tend to be restricted to certain areas. Various species of Culicoides midges are required as vectors. Replication of the virus has to occur in the vector. Serotype 8 first came to northern Europe in 2006 and caused the birth of ‘Dummy type’ calves. BTV is primarily a disease of sheep and goats, but the first recorded case in the UK was in a cow. Normally the virus is asymptomatic in cattle except for causing abortions and stillbirths with central nervous system (CNS) defects. If there are signs of clinical disease in cattle they are caused by endothelial damage and disseminated intravascular coagulation (DIC), and are shown as haemorrhage, ischaemia, inflammation and oedema. The lesions are common in areas subject to mechanical trauma and abrasion, e.g. the feet, mouth and eyes. There is fever up to 42°C. The diagnosis is confirmed by PCR for viral RNA. It can detect all 24 serotypes. There is no specific treatment for BTV. Antibiotics and non-steroidal anti-inflammatories (NSAIDs) are helpful. Nursing is vital and should include offering water and mushy food, and providing deep bedding out of the sun and heat. There are vaccines available which are monovalent for each serotype. Cattle require two doses separated by 2 weeks.
Bovine malignant catarrh (BMC)
This disease is rare in the UK but seasonally common in East Africa. It is caused by a group of herpesviruses, which include Alcelaphine herpesvirus 1, Ovine herpesvirus 2 and Caprine herpesvirus 2. The most important is Alcelaphine herpesvirus 1 which is carried asymptomatically by the wildebeest (gnu) in East Africa. In the UK, the sheep is the asymptomatic carrier. Affected cattle will have a high fever and acute ocular discharge with corneal opacity and erosions causing a high mortality. Treatment is hopeless. Differentiation from bluetongue and mucosal disease may be difficult clinically. Diagnosis is either with an ELISA or a PCR. There is no vaccine available.
Bovine papular stomatitis
This is a mild disease of calves which exhibits raised papules in the mouth and is caused by a Parapoxvirus. There are no lesions seen on the coronary band. The disease is self-limiting and there is no treatment or vaccine available. It is only important in case it is confused with FMD. See also the section on ‘Viral skin diseases’ under ‘Diseases of the Integument’ below.
Bovine viral diarrhoea (BVD)
BVD type 1 disease, caused by Bovine viral diarrhoea virus 1 (BVDV 1) is normally associated with reproductive problems in adult cattle. There is also a BVD type 2 disease which can cause acute illness in cows and is usually fatal. The cows feel ice cold to the touch and have a low rectal temperature. They have profuse watery diarrhoea and death follows in a few hours. There is no treatment but there is a vaccine.
Cows infected with BVD type 1 during very early pregnancy will reabsorb the embryo and return to service. Cows infected in early and middle pregnancy will produce calves which are persistently viraemic (i.e. persistently infected (PI) calves). These calves may develop mucosal disease, which is invariably fatal. The calves or yearlings will be ill, sometimes with a fever. They will have erosions around the mouth and will be totally anorexic. A heparinized blood (Green top Vacutainer) test will reveal virus positive animals, i.e. PI calves, even before they manifest clinical disease.
See also ‘Bovine viral diarrhoea virus (BVDV)’ as a cause of abortion under ‘Diseases of the Reproductive System’ below.
Coronavirus
This virus causes scouring in young calves and is implicated in causing ‘winter dysentery’ in adult cows. ‘Winter dysentery’ is misnamed as dysentery and is rare, but explosive diarrhoea will be seen in virtually the whole herd. There is no treatment or vaccine but recovery is swift. Coronavirus is commonly associated with scouring in calves. It can be confirmed by an ELISA on the faeces. Treatment is symptomatic, as well as using oral antibiotics to help the secondary infections. There is a vaccine for calves which can be given to cows 6 weeks before parturition to boost passive immunity.
There is also a vaccine which can be given orally directly to calves within 6 h of birth.
Foot-and-mouth disease (FMD)
This highly contagious disease is caused by an Aphthovirus. There are seven immunologically distinct serotypes; A, O, C, Asial, South African Type (SAT) 1, 2 and 3. The signs will vary markedly in severity with the strain of virus, the breed of animal and the type of husbandry. The earliest signs are vesicles -fluid-filled sacs within the epithelium on the tongue, buccal mucosa and coronary band. There is marked excess salivation, lameness and pyrexia. There are vaccines available for all serotypes.
Rotavirus
Rotavirus is the most common virus causing scouring in calves worldwide. The disease has a high morbidity and a very low mortality. Diagnosis is confirmed by a PAGE test on the faeces. Treatment is symptomatic, i.e. by rehydration, as well as using oral antibiotics to help the secondary infections. There is a vaccine which can be given to cows 6 weeks before parturition, and passive immunity can be boosted