Evidence of co-infection with Mycobacterium bovis and tick-borne pathogens in a naturally infected sheep flock

Mycobacterium bovis (M. bovis) has an exceptionally wide host range including sheep. Information on tuberculosis (TB) in sheep is scarce, and there appears to be conflicting opinions about the relative susceptibility of sheep to infection. In Ethiopia, there was no single previous report on tuberculosis in sheep, though mixed farming of cattle and sheep is a common practice. In this study, following the observation of TB-like lesions on sheep died from sheep flock kept in contact with cattle herd, further investigation was conducted on the flock to assess the magnitude of the infection and identify and characterize the causative M. bovis strain. An outbreak investigation was carried out on 26 eligible sheep out of 33 sheep found on the farm. Comparative intradermal tuberculin (CIDT) test, postmortem examination, Mycobacterium culturing, and spoligotyping were the techniques used in the study. The prevalence of TB in the tested sheep was 15% (4/26). All the sheep that were positive to CIDT had gross lesions suggestive of TB. Three of the positive sheep had extensive and multiple lesions. M. bovis was isolated from all four sheep and the strain was identified as spoligotype SBO134. The in-contact dairy cows were screened for TB and 98% (45/46) of the cows tested positive to CIDT. Furthermore, the same strain, SB0134, was also isolated from the two in-contact cows. The isolation of a matching genotype (SB0134) of M. bovis from both species sharing a known epidemiologic link strongly suggests that the sheep flock might have acquired the pathogen from the dairy cows. This warrants strict physical separation of the sheep flock from the cattle herd to prevent such interspecies transmission of M. bovis.

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Characterization of Anaplasma phagocytophilum and A. ovis infection in a naturally infected sheep flock with poor health condition

Tropical Animal Health and Production ◽

10.1007/s11250-010-9580-8 ◽

2010 ◽

Vol 42 (7) ◽

pp. 1327-1331 ◽

Cited By ~ 29

Author(s):

Alessandra Torina ◽

Ruth C. Galindo ◽

Joaquín Vicente ◽

Vincenzo Di Marco ◽

Miriam Russo ◽

...

Keyword(s):

Anaplasma Phagocytophilum ◽

Health Condition ◽

Infected Sheep ◽

Poor Health ◽

Sheep Flock

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Vaccination delays maedi-visna lentivirus infection in a naturally-infected sheep flock

BMC Veterinary Research ◽

10.1186/1746-6148-9-16 ◽

2013 ◽

Vol 9 (1) ◽

pp. 16 ◽

Cited By ~ 4

Author(s):

Margrét Gudnadóttir ◽

Andreas Demosthenous ◽

Theophanis Hadjisavvas

Keyword(s):

Infected Sheep ◽

Sheep Flock

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Population dynamics of scrapie in a sheep flock

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1999.0427 ◽

1999 ◽

Vol 354 (1384) ◽

pp. 751-756 ◽

Cited By ~ 19

Author(s):

M. E. J. Woolhouse ◽

L. Matthews ◽

P. Coen ◽

S. M. Stringer ◽

J. D. Foster ◽

...

Keyword(s):

Clinical Signs ◽

Infected Sheep ◽

Sheep Flock ◽

Sheep Population ◽

Long Duration ◽

Environmental Reservoir ◽

Natural Scrapie ◽

Available Information ◽

Parameter Values

A detailed analysis of an outbreak of natural scrapie in a flock of Cheviot sheep is described. A total of 137 cases was reported over 13 years among 1307 sheep born into the flock. The epidemiology of scrapie can only be understood with reference to sheep demography, the population genetics of susceptibility to scrapie, pathogenesis during a long incubation period, and the rate of transmission (by both vertical and horizontal routes), all of which interact in complex ways. A mathematical model incorporating these features is described, parameter values and model inputs are derived from available information from the flock and from independent sources, and model outputs are compared with the field data. The model is able to reproduce key features of the outbreak, including its long duration and the ages of cases. The analysis supports earlier work suggesting that many infected sheep do not survive to show clinical signs, that most cases arise through horizontal tranmission, and that there is strong selection against susceptible genotypes. However, important aspects of scrapie epidemiology remain poorly understood, including the possible role of carrier genotypes and of an environmental reservoir of infectivity, and the mechanisms maintaining alleles giving susceptibility to scrapie in the sheep population.

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