Paratuberculosis:

Synonyms: Johne’s Disease, Chronic bacillary dysentery

• It is chronic infectious fatal gastrointestinal disease of ruminants.
• It is characterized by progressive emaciation and diarrhoea. Lesion in intestinal mucosa give a velvety appearance with thickening and corrugation of the wall.
• Lymphnodes becomes enlarged and edematous.
• This disease was first described by German veterinarian in dairy cow in 1895. So, disease was named after him.

Etiology:

• Mycobacterium paratuberculosis
• Organism is small, acid fast bacillus.
• It is strictly aerobic, non-spore forming, non-motile gram-positive organism.
• Organism can be demonstrated in the tissue section stained by Z-N stain.

Epidemiology:

• Disease is widely prevalent in cattle and has been distributed globally.
• Disease has been reported from Africa, Australia, Belgium, Congo, Canada, France, New Zealand, USSR, Uruguay, Palestein, Sumatra, Pakistan, India, Bangladesh and Nepal.
• Bovine is highly susceptible but other ruminants like sheep, goat, and buffalo are also susceptible.
• Disease has been occasionally recorded in horse, mule, and pig.
• Animals less than one month are most susceptible to infection.
• High yielding dairy cattle are highly susceptible and shows severe manifestation.

Transmission:

• Natural infection occurs through the way of alimentary tract when the calves are very young.
• Contaminated food and water with faecal materials are potential ways of transmission.
• Calves acquire infection in their intra-uterine lives.
• Young calf may contract the infection while suckling the teats.
• Direct contact with infected cattle.

Pathogenesis:

Clinical Findings:

• IP: 4 months-15 years
• Most cardinal clinical sign is diarrhoea. It is intermittent or continuous in nature.
• Animal remains unthrifty with dry coat and without fever.
• Appetite may be retained.
• Feces is dark in color and contain bubbles. As a result of continuous diarrhoea, animal becomes hide bound.
• Progressive loss of body weight.
• Loose skin develops in intermandibular space, dewlap and brisket region stimulating edema.
• Color of the hair turn fade. In later part of disease, animal becomes extremely weak and recumbent.
• Animal takes less food and water.
• In sheep and goat, diarrhoea is absent but the feces remain soft and emaciation is observed.

PM Findings:

• Carcass is extremely emaciated.
• Characteristic lesion is noted in caecum and colon, which are red and edematous.
• There is diffuse thickening along with transverse and longitudinal corrugation of intestinal wall-making irregular folds.
• Surface of fold are red but not ulcerated.
• There is no nodules like tuberculosis.

Diagnosis:

• Based on clinical findings
• Intradermal Johnin test: 0.1-0.2 ml of Johnin is given on one side of the neck. Change in skin thickness greater than 5mm is considered positive after 24-48 hours.
• Intravenous Johnin test: It provides greater accuracy but each test needs 2-4 ml of Johnin. Rise of body temperature to 1.5°C is considered as positive reaction.
• Complement fixation test
• HA test
• AGID
• ELISA
• FAT
• Biopsy of lymph node
• Fecal culture; Herrold’s egg yolk media (HEYM) can be used for culture. It required 3-4 weeks for cultivation.

Treatment:

• There is no satisfactory treatment available. However, antitubercular drugs like streptomycin sulphate @50mg/kg, b.wt. OD, IM for 2-3 weeks has been used.
• Streptopenicillin @10,000 IU/kg, b.wt. OD, IM for 2-3 weeks
• Combination of 500mg of Dihydrostreptomycin IM and 300 mg Rifampin with 300 mg isoniazid, PO, BID provide some improvement in goat.
• Sulpha bolus; 2 bolus, BID, 2-3 weeks in large animals and half bolus, BID for 2-3 weeks in small animals.

Control Measures:

• All animals of enzootic zone should be tested by fecal culture method once in 6 months.
• Animals that are positive in fecal culture should be disposed off either by slaughter in case of sheep and goat.
• Feedlots and paddocks must be ploughed and covered with fresh soil.
• Stagnant water must be drained away.
• Offsprings must be removed immediately following parturition.
• Colostrum may be effectively boiled before feeding.
• Transportation of contaminated faeces should be avoided.
• Animal should be allowed to graze on pasture which is not infected.
• Movement of animal from infected areas to non-infected zone should be restricted.
• Surroundings and utensils should be thoroughly disinfected.
• Proper disposal of dung should be undertaken since it is the main source of infection.
• All newly purchased animals should be tested before allowing them to mix with other members of the herd.
• Vaccine consisting of live non-pathogenic strain of M. paratuberculosis with equal parts of liquid paraffin and olive oil with little finely powdered pumice stone is administered SC to calf. Dose: 1.5 ml