MORPHOLOGICAL STUDIES ON THE TICK FAUNA OF GOATS AND DETECTION OF ACARICIDE RESISTANCE
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Date
2019
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College of Veterinary and animal Science,Mannuthy
Abstract
A comprehensive study of the morphology of different species of ticks
under light and electron microscopy and detection of acaricide resistance status
among ticks infesting goats in Kerala was done. A total of 1200 ticks were
collected from goats that were reared in 13 organised and unorganised farms of
Thrissur and Palakkad districts of Kerala as well as from those presented to
University Veterinary Hospital at Mannuthy and Kokkalai. It was observed that
ear pinna was the most preferred site for tick attachment followed by tail, head,
eyes, neck region. Gross morphological features were observed by light
microscopy and four tick species under the genus Haemaphysalis and two species
under the genus Rhipicephalus were identified. Out of the 1200 ticks examined,
1190 ticks (99.1 per cent) belonged to Haemaphysalis genus and 10 ticks (0.83
per cent) to Rhipicephalus genus. Among the genus Haemaphysalis, the most
prevalent species on goats was H. bispinosa (63.02 per cent), followed by H.
intermedia (36.55 per cent), H. megalaimae (0.25 per cent) and H. kutchensis
(0.16 per cent). Among the genus Rhipicephalus, R. haemaphysaloides (50 per
cent) and R. sanguineus (50 per cent) were identified. The present study reports H.
megalaimae and H. kutchensis for the first time in Kerala. Ultrastructural
morphology of external surface of Haemaphysalis spp. was studied by scanning
electron microscopy. Larval packet test was used to detect acaricide resistance for
deltamethrin and amitraz against Haemaphysalis spp. the most prevalent tick
infesting goats. In the present study, Ottapilavu, Mundupalam and Poomala
isolates were found susceptible, while Vadakkanchery isolate was resistant. All
the tested population viz., Mundupalam, Poomala, Vadakkanchery and Choondal
isolates of Haemaphysalis spp. were susceptible to amitraz. Log probit analysis
was done to derive the LC50 and LC90 of resistant and susceptible isolates. Adult
immersion test was performed to assess the status of resistance to deltamethrin
and amitraz in Haemaphysalis spp. isolates from Thrissur and Palakkad districts.
The per cent mortality and reproductive indices were measured at different
concentrations as well as at discriminating dose. In the present study, Ottapilavu
isolates of Haemaphysalis survived upto 240 ppm deltamethrin and was
considered resistant. The per cent mortality in Amaloor isolates was 90 per cent at
120 ppm and hence was considered resistant. The predicted mortality at 75 ppm
for Vennur isolates was 91 per cent and was considered susceptible. Log probit
analysis was done to derive the LC50 and LC90 of resistant and susceptible
isolates. It was observed that as the concentration of deltamethrin increased, the
reproductive index decreased and the oviposition was inhibited. At 240 ppm there
was only approximately 55 per cent inhibition of oviposition in resistant
Ottapilavu isolates, while in Amaloor isolates 100 per cent inhibition was
recorded. All the isolates in the present study were susceptible to amitraz.
Haemaphysalis spp. on goats are developing resistance to deltamethrin. Amitraz
may be recommended for tick control in goats in areas where deltamethrin
resistance has been observed. Future investigations are to be conducted on
molecular characterisation of resistance in these species of ticks as well as to
detect the status of resistance to different group of acaricides throughout the state.