STUDIES ON MOLECULAR EPIDEMIOLOGY OF BRUCELLOSIS AND TUBERCULOSIS IN CATTLE AND BUFFALOES
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Date
2020-09
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
Brucellosis and tuberculosis are neglected zoonoses having worldwide public
health concern. The present study was undertaken to elucidate the prevalence of
brucellosis and tuberculosis in cattle and buffaloes, detect and identify the species by
PCR, understand the genetic diversity among the detected species, investigate the
antimicrobial resistance of pathogens and evaluate the risk factors associated with the
occurrence of these diseases.
A total of 1070 samples comprising of 330 blood samples, 185 milk samples,
310 nasal swabs and 245 vaginal swabs from 300 cattle and 30 buffaloes which were
reared along with cows were collected and examined for detection of brucellosis and
mycobacteriosis in different production systems viz., intensive (110), semi-intensive
(110) and extensive system (110). The overall prevalence of brucellosis and
mycobacteriosis was 6.06% (20/330) and 3.33% (11/330), respectively among the
animals studied. The prevalence of both the diseases was higher in farms with
intensive production system and larger herd size. Sexually active (2-10 years) and
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aged animals (5-10 years) were at risk of infection for brucellosis and tuberculosis,
respectively. Exotic breeds of cattle were more susceptible to mycobacteriosis
compared to indigenous breeds.
Rose bengal plate test (BPT) and indirect enzyme linked immunosorbent
assay (iELISA) tests revealed almost perfect agreement (К=0.92) with each other.
While, SIT and IFN-γ ELISA tests revealed substantial agreement (К=0.50) with each
other. The species of Brucella recognized by Bruce-ladder multiplex PCR in cattle
were found to be B. melitensis (4) and B. abortus (5) out of 09 samples confirmed by
PCR. Further, all the Mycobacterium spp. detected by PCR were differentiated as non
tuberculous Mycobacterium (NTM) by commercial qPCR kit. Brucella species
displayed genetic homogeneity by both PCR-Restriction Fragment Length
Polymorphism (RFLP) and Repetitive Element Palindromic (REP)-PCR techniques.
Multiple Antimicrobial Resistance (MAR) index for B.abortus and B.
melitensis isolates were found to be in the range of 0.66 to 0.83 and 0.5 to 0.91,
respectively. Majority of the isolates showed the presence of multiple genes
responsible for resistance to rifampicin (rpoB-M4, M5, M6 and +354rB/-720rB gene)
fluoroquinalones (gyrA and gyrB). While only one isolate showed the presence of
single gene (tetB) responsible for resistance to tetracyclines and one isolate showed
presence of single gene {Aac(3)-Ia} responsible for resistance to aminoglycosides.
None of the isolates showed presence of catB gene responsible for resistance to
chloramphenicol even though all the isolates were resistant to chloramphenicol
phenotypically. There was significant association with the individual level (age, sex
and breed) and herd level risk factors (production system, herd size, cleanliness and
lack of screening of animals) with the occurrence of brucellosis and mycobacteriosis
in cattle and buffaloes as evidenced by Odd’s ratio.
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