LABORATORY ANIMAL MEDICINE

Introduction  Laboratory animals are animals used in the laboratory for scientific researches e.g.  Rabbit, mouse, Rat, Guinea pigs, Hamsters, Girbils etc.  Lab animal medicine is more of prevention than curative. It is easier to prevent diseases than to cure.  When not prevented, the diseases can kill a whole colony of pets or research animals  Involves good management e.g. hygiene, good, balanced diet, good and adequate housing(free from draught, dampeness, direct sunlight and extreme temperatures.)

(a)INFECTIOUS MYXOMATOSIS: Caused by a poxvirus.  Characterized by high mortality (40-100%). It occurs as fibromas.  Enzootic in Eastern and Western United States, Europe, South America and Australia.  The situation in Africa is still unknown.  Transmitted mechanically by o Mosquitoes and biting insects e.g. fleas o Direct contact from the cotton tail to domestic rabbits where the disease ranges from peracute, fatal to transitory and single fibromas.

Clinical Signs  All ages are susceptible but younger ones (1 month – 1 year) are less susceptible.  Characterized by conjunctivitis with milky ocular discharges listlessness, anorexia, fever (108 0 F).  In severe cases death may occur within 48 hours.  Survivors after this become progressively, depressed, develop rough coat, edematous eyelids, nose, lips and ears giving rise to the characteristic “big head”.  Edematous and inflamed vent in the male, the scrotum becomes swollen.  Drooping ears due to edema.  Purulent nasal discharges and laboured respiration followed by coma and death which usually occurs 1-2 weeks after the appearance of clinical signs.

 Diagnosis o Clinical signs, Virus isolation and serology  Treatment o None  Control and prevention o Control of vectors o Quarantine of new animal in insect proof quarters for 2 weeks. o Vaccinate animals with a live attenuated myxomatosis virus vaccine.

BACTERIAL DISEASES Common in domestic rabbits. PASTEURELLOSIS o Snuffles o Enzootic pneumonia o Otitis media o Genital infection o Abscesses o Conjunctivitis o Septicaemis o Pyometra o Orchitis

1)Snuffles (Nasal catarrh) Aetiology: Pasteurella multocida Characterized by  Rhinitis, pneumonia, otitis media and conjunctivitis.  Used to describe rhinitis and paranasal sinusitis characterized by serous, mucous or mucopurulent nasal discharges.  Usually complicated by such bacteria as Staph. aureus and Bordetella bronchiseptica.  Symptomatic carriers may come down due to stress (change in weather, pregnancy, concurrent diseases, experimentation)  Spread is by direct contact or through aerosol.

Clinical Signs  May be acute, subacute or chronic characterized by nasal discharges which may be serous, mucous or mucopurulent.  Sick rabbits paw with the inside of the front legs causing matting of the fur around that area, sneezing coughing are usual.  Snuffles is common at kindling period or during low resistance.  Death may occur while recovered animals become carriers. Treatment  Penicillin and streptomycin, Sulphaquinoxaline, furazolidone may be administered.

2. ENZOOTIC PNEUMONIA  Aetiology P. multocida  Usually complicated by other bacteria like o klebsiella pneumomae, o Bordetella bronchiseptica o Pneumococci.

Clinical signs  Starts with nasal infection, anorexia, fever (40 0 C) dyspnea.  There may be diarrhea and weakness.  Death may occur within 4 days.  Some animals may die without showing clinical signs. Treatment  As for snuffles. Tetracyclines may be used.

OTITIS MEDIA  P. Multocida is the usual causative agent but Staph spp and Bordetella spp may also be found. o Transmission is by o direct contact, o formites  respiratory route

Clinical signs:- Torticollis. In severe cases the rabbis may not be able to eat or drink resulting in weight loss and dehydration. If the meninges are affected incordination and other nervous signs may occur. Treatment Tympanocentesis plus antibiotic (antibiotic alone may not be effective).

GENITAL INFECTION  Caused mainly by P. multocida complicated by other organisms.  Common in adults, more common in does than in bucks.  Transmission is through coitus.

 Clinical signs o May be acute or subacute inflammation of the reproductive track. o Causes pyometra in females characterized by mucoid vaginal discharges. o It may also be purulent, thick yellowish-grey in colour. o In bilateral cases there is sterility but if only one horn is affected there may be normal litter. o In the male a purulent penile discharge, orchitis also occurs.  Treatment o Antibiotics which may be of little value. Ovariohysterectomy in pets plus antibiotic.  Control o Cull all affected animals. o Regularly examine the genitalia of breeding stock. o Bucks with low conception rate should be culled also females that consistently fail to conceive.

ABSCESSES P. multocida predisposed by wounds which may result from light by males, scratches from other rabbits or sharp wire from the cage. Clinical signs Subcut swelling, abscesses of internal organs which may result in septicaemia and death. Treatment Lancing and draining antibiotic treatment both topically and systemically. Control Eliminate affected animals, remove predisposing factors.

CONJUNCTIVITIS o Caused by P. multocida, other organism may be incriminated. Common in young ones than in adults but both are quite susceptible.  Clinical signs o Swollen eye lids gumed together by exudates. o Inflamed conjunctiva, mucoid later mucopurulent ocular discharges. Affected animals rub the eyes with their front legs. o Inflammation may become chronic with edema subsiding but discharges continue resulting in epiphora. o Pathological overflow of tears on to the cheek.  Treatment o Penicillin or chloramphenicol eye ointment.

 SEPTICAEMIA o Caused by P. multocida:- may be from other Pasteurella infection.  Clinical signs o May not be detected as the animal dies suddenly but may be noticed if other forms of pasteurellosis have been incriminated.  Treatment o Usually not practicable as animal dies suddenly.  Control:- o Avoid infection by P. multocida, eliminate affected animal. Prevent stress.

PARASITIC DISEASE Coccidiosis  Major intestinal but self limiting disease of rabbit Recovered animals become carriers.  There are two forms of the disease in rabbit, liver and intestinal coccidiosis.  Liver form is caused by Eimeria stiedae  The intestinal form is caused by a variety of spp – E. megna, E. irresidua, E. media, E perforans.  Nasal coccidiosis is due to contamination of mucous membranes of the nose while practicing coprophagy. Clinical signs  Older animals may be able to cope with the infection but become carriers. The young ones succumb easily.

Hepatic coccidiosis:- There may be no clinical signs but severe infection results in cachexia, abdominal distension and death as a result of hepatic dysfunction. Intestinal coccidiosis Vary from inapparent to poor weight gain. May be acute or chronic. Common signs are enteritis, diarrhea which may be unformed stool or watery, catarrhal or bloody fluid. In acute cases there is rapid weight loss severe dehydration, polydipsia, anorexia but at times with ravenous appetite. In some cases when young ones are affected with virulent organisms e.g. E. irresidua or E magna may die with no clinical signs.

Diagnosis is based on finding oocysts in the faeces but there could be oocysts without clinical signs. In case of sudden death oocysts may not be seen but all the stages may be found in the intestinal mucosa. Treatment Sulphamerazine 0.02% in drinking water Sulphaquinoxaline 0.05% in drinking water or 0.03% in feed (for 2 weeks). Control Hygiene, eliminate carriers, screen incoming rabbits for oocysts. Avoid contamination of food and water with faeces. Separate the young ones from the adults.