FORMULATION OF A COMBINED TARGETED SELECTIVE TREATMENT STRATEGY FOR SUSTAINABLE CONTROL OF GASTRO INTESTINAL NEMATODOSIS IN GOATS
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Date
2020-12-18
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES, MANNUTHY, THRISSUR
Abstract
Gastro intestinal parasitism and mounting anthelmintic resistance pose
serious impediments to goat production in humid tropical state of Kerala. In order
to develop a sustainable parasitic control strategy ideal for goats of the state, a
comprehensive research on epidemiology of gastro-intestinal parasitism,
parasitological indicators and helminth control modules was carried out with the
following objectives; 1) conduct a survey on epidemiology and current treatment
strategies of gastro-intestinal parasitism among goats in Kerala; 2) validate the
combined targeted selective treatment (C-TST) indicators such as FAMACHA©,
body condition score (BCS) and dag score (DS); 3) compare the impact of
treatment strategies like routine anthelmintic treatment (RT), strategic
prophylactic treatment (SPT) and C-TST on the growth performance and
anthelmintic resistance in goats; and 4) develop an anaemia eye colour chart based
on the physiological status suitable for goats in humid tropics.
Detailed survey on veterinary practitioners in Kerala on their awareness on
parasite control practices revealed that updates on advances in veterinary
parasitology in relation to dose calculation, development and management of
anthelmintic resistance and alternate methods of parasite control with limited
chemotherapy need to be intensified. A glance into the parasite management
strategies followed by the goat farmers of Kerala indicated that majority of them
were clueless of the importance of correct dosage, frequency of anthelmintic
treatment and integrated parasite management methods.
Epidemiological survey of gastro-intestinal parasitism in goats in the state
was carried out in 13 agro-ecological zones for a period of one year in six
organised farms and 120 small holder flocks. It revealed an overall prevalence of
67.2 per cent strongylosis with a mean faecal egg count (FEC) of 390.79 ± 19.17,
ranging from 0 to 8968 and standard deviation of 716.745. Highly significant
influence of season and month (p 3, BCS was ≤ 1.5, dag score was ≥ 2 and/ or FEC >500. In the case of
routine treatment bimonthly anthelmintic treatment was carried out whereas in the
case of strategic prophylactic treatment (SPT) anthelmintic treatment was given
before South West monsoon (June) and after North East monsoon (October).
After 13 months of treatment, the impact of the C-TST on parasitological and
production parameters and mortality was assessed. More number of doses (256)
were required for the RT while for SPT only 152 doses were required for
administration. The least number of doses (82) only were given to animals in C TST, where treatment was applied based on the TST indicators. The impact of the
C-TST on anthelmintic resistance was assessed by FECRT and molecular
methods, and no statistically significant difference was detected before and after
treatment and between the treatment groups. There was no significant difference
in prolificacy, weight gain and mortality between C-TST and the other two
treatment regimes. .
Molecular genotyping of Haemonchus contortus by PCR-RFLP revealed
the presence of polymorphism at 198 and 200 codons, while at codon 167 no
heterozygous genotype were detected. In Trichostrongylus sp. F200Y
polymorphism was identified in isotype 1-β tubulin, whereas at codon 167 only
resistant genotypes were detected. The gene frequency was 0.16 for resistant
allele before treatment and 0.14 after treatment. In this species, no polymorphism
was detected at E198A in all the treatment categories. The most frequently
identified polymorphism in H. contortus was associated with E198A, while
F200Y was found to be the least common. In Trichostrongylus sp., F200Y was
found to be the most common. No significant difference could be observed
between the genotype frequencies at the three codons in the two species of
strongyle parasites before and after treatments.
Description
Submitted in partial fulfillment of the requirement for the degree of
DOCTOR OF PHILOSOPHY in Veterinary Parasitology