ijvp

Indian Journal of Veterinary Pathology

0250-47580973-970X

Indian Association of Veterinary Pathologists

ijvp-31-2-abs008

ABSTRACTS OF DISSERTATIONS OR ARTICLES

Experimental paratuberculosis in rabbits and mice.

Jolhe

D.K.

¹Tripathi

B.N.

Dr¹

¹Degree/Year: Ph.D/2008 University: Deemed University, IVRI, Izatnagar-243 122, UP.

1122007

312191191

2007

IndianJournals.com

Fifty four rabbits (New Zealand White) and 54 BALB/c mice aged 2–4 weeks were divided into 3 groups viz. oral, intraperitoneal and intravenous with 12 animals each and their respective control groups with 6 animals each. The bovine isolate was grown in Middlebrook 7H9 medium with ADC and mycobactin J, harvested and final concentrations of 10⁸, 10⁷ 10⁶ and 10⁵ cfu per inoculum suspended in pasteurised milk for oral (10 times), and in sterile saline for I/P and I/V inoculations (3 times), respectively for rabbits and mice. The infection was monitored for a period of 9 months by serological, immunological, bacteriological, molecular and sequential pathological methods at 3 time points (3, 6 and 9 months post infection).

In rabbit experiment, most rabbits in all the 3 groups did not exhibit any clinical signs except rough hair coat, depletion of perineal and mesenteric fat reserve, and emaciation and decrease in the body weight at 9 MPI in I/V group. No gross lesion suggestive of paratuberculosis infection was observed in any group. Histologically, the I/V group had more pronounced lesions in the organs such as ileum, sacculus rotundus, vermiform appendix and mesenteric lymph nodes. Focal to multifocal granulomas were observed in the lymphoid follicles of these organs. The oral and I/P groups did not have significant differences in terms of type and severity of the lesions which were produced in the ileum, sacculus rotundus, mesenteric lymph nodes and vermiform appendix but lesions were less pronounced than the I/V group. The acid-fast bacilli were observed in the sacculus rotundus and mesenteric lymph nodes of 2 rabbits from I/V group at 9 MPI. There was rising antibody titres in all the groups from 3 MPI onwards but was most prominently observed in the I/V group. None of the rabbits from any group reacted positively to intradermal johnin skin test at any time point. MAP was isolated from tissues of one rabbit each at 3 and 6 MPI from I/V group. Faecal shedding by bacterial culture was not detected in any rabbit of the 3 groups. Faecal and tissue PCR results were positive at 6 MPI for all the 3 groups.

In mice experiment, clinical symptoms such as depletion of perineal and mesenteric fat reserve, muscle wasting, emaciation and unthriftiness were observed more frequently in IP &IV groups than the oral group mice. In addition, decrease in the body weights in one mouse of oral group at 6 MPI and 2 and 1 mice of IV and IP groups, respectively at 9 MPI were also observed. Gross lesions suggestive of paratuberculosis infection were not observed in any group. Histologically, the small intestine particularly ileum showed broad, flat and fused villi with increased infiltration with lymphocytes and macrophages without formation of distinct granuloma in lamina propria from 3 to 9 MPI in all the 3 groups. Distinct granulomas were observed mostly in the lymphoid tissues. The large intestine particularly caecum revealed increased macrophage infiltration in the mucosal layer. The mesenteric lymph nodes revealed multifocal granulomas at 9 MPI in the oral group, whereas animals from I/P and I/V groups had multiple granuloma at 6 and 9 MPI. The liver in the oral group showed only a few small aggregates of lymphoid cells, in the I/P group 12 focal granulomas, whereas in the I/V group, it had focal to multifocal granulomas from 3–9 MPI. The acid-fast bacilli were detected in the mesenteric lymph nodes of only one mouse from I/V group at 9 MPI. Serologically, there was rising titres of antibodies to MAP most prominently in the oral than in the I/P and I/V groups in the ELISA. None of the mice of three groups reacted positively to intradermal johnin skin test. Faecal excretion of the bacteria was not detected in culture. Only one mouse was found positive in tissue culture at 9 MPI from I/V group. One mouse each in I/P and I/V groups at 3 MPI in tissue PCR, and one mouse each in oral and I/V groups at 6 MPI were found to be positive in the faecal PCR.