Abstract
A total of 355 cows were sampled (serum, n = 315; faeces, n = 355; milk, n = 209) from dairy farms located in the Punjab state of India. Faeces and serum/milk samples were screened by acid fast staining and “indigenous ELISA,” respectively. IS900 PCR was used to screen faeces and milk samples. Bio-load of MAP in dairy cows was 36.9, 15.6, 16.3, and 14.4%, using microscopy, serum ELISA, milk ELISA and milk PCR, respectively. Estimated kappa values between different test combinations: serum and milk ELISA, faecal microscopy and faecal PCR, milk ELISA and milk PCR, faecal PCR and serum ELISA were 0.325, 0.241, 0.682, and 0.677, respectively. Estimation of the relative sensitivity and specificity of different tests in the present study indicated that “serum ELISA” and “milk ELISA” were good screening tests, add “milk PCR” was “confirmatory test” for MAP infection. Combination of milk ELISA with milk PCR may be adopted as a model strategy for screening and diagnosis of JD in lactating/dairy cattle herds in Indian conditions.
Highlights
Johne’s disease (JD) is a chronic progressive incurable granulomatous enteritis of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP)
Thirty dairy farms located in different parts of Punjab state (India) were randomly selected and from each farm a minimum of 10 cows were sampled for blood, faeces, and milk
Whey was curdled with 3.0% citric acid and centrifuged at 5000 rpm for 30 minutes to collect clear whey, which was stored at −20∘C till further use for the presence of MAP antibodies by “Indigenous ELISA Kit” [9]
Summary
Johne’s disease (JD) is a chronic progressive incurable granulomatous enteritis of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). Indian studies showed consistently high bio-load of the disease in large ruminants [1]. Recovery of MAP from human breast milk [4] and gut [5] increased the concern for the control of disease in animals. And accurate diagnosis is the prerequisite for the control of infection thereby improving the sustainability and productivity of Indian dairy herds [7]. Reports on the bio-load of MAP using milk as the test sample are scanty [8]. Study aimed to evaluate sensitivity and specificity of different diagnostic tests to estimate bio-load of MAP in dairy herds in Indian husbandry conditions
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