MORPHOLOGICAL AND MOLECULAR IDENTIFICATION OF VISCERAL SCHISTOSOMES IN BUFFALOES OF ANDHRA PRADESH
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Date
2023-04
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
The present study was undertaken to determine the prevalence of visceral
schistosomosis caused by Schistosoma species in Andhra Pradesh. For this, a total of 467
slaughtered buffaloes mesenteries and livers collected from abattoirs of Krishna district
were sampled for a period of one year. On examination, 95 buffaloes were found to be
infected with Schistosoma species giving an overall prevalence of 20.34%. The prevalence
of schistosomosis was significantly (P<0.001) higher in adults (>2.5yr; 31.95%) than in
young (<2.5yr; 13.75%) animals and non-significantly high in females (26.02%) than in
males (19.28%). The prevalence was significantly (P<0.001) high during rainy season
(28.47%) followed by winter (21.73%) and summer (10.96%) seasons. Month wise
prevalence of schistosomosis in the study area revealed highest prevalence of
schistosomosis in July (34.21%) and lowest prevalence during May (5.88%). Most of the
infections were mild (48.42%) followed by moderate (36.84%) and severe (14.73%)
infection. Mild to moderate infections were noticed in young animals and severe infection
was noticed in adults. The worms were milky white in colour. Male worms were stout and
carried the females in a groove like a gutter i.e, gynaecophoric canal. Based on three to six
testicles, a smooth cuticle, a conical projection at the back of the male, and spindle-shaped
eggs in the female's uterus the worms were identified as Schistosoma spindale. Grossly
infected livers showed petechiae to patchy haemorrhages, necrotic foci, and whitish worms
entrenched in portal veins. The serosal surface of the small intestines had white grey
nodules and moderate haemorrhages with necrotic foci on the mucosa. The liver sections
revealed moderate to severe congestion of blood vessels and mild degenerative changes in
hepatocytes along with adult flukes in the central veins and capillaries of sinusoidal spaces.
Infected intestines displayed moderate to severe congestion of blood vessels, haemorrhages
in mucosa and the cut section of the parasite in the muscularis mucosa. Few sections of
liver and intestine were evident with fibrous tissue proliferation surrounding the parasitic
ova and development of microgranulomas. Trabecular thickening, and haemosiderin
engulfed macrophages were present in mesenteric lymph nodes along with degenerated
parasitic ova. The morphologically identified adult fluke were confirmed through
amplification of 28S rRNA gene that yielded 330bp product specific for S. spindale. The
sequencing and blast analysis of two S. spindale AP isolates revealed 100% homology with
Asian populations of S. spindale. Results confirm that schistosomosis is endemic in
buffaloes in Andhra Pradesh