Biology subjects

Abbas, K.

Publications and source records attributed to Abbas, K..

3 recordsLinked to original sources

bioRxiv2023

Indigenous cattle of Sri Lanka: Genetic and phylogeographic relationship with Zebu of Indus valley and South Indian origin

The present study reports the population structure, genetic admixture and phylogeography of island cattle breeds of Sri Lanka viz. Batu Harak, Thawalam and White cattle. Moderately high level of genetic diversity was observed. Estimates of inbreeding for Thawalam and White cattle breeds were relatively high with 6.1% and 7.2% respectively. Genetic differentiation of Sri Lankan Zebu (Batu Harak and White cattle) was lowest with Red Sindhi among Indus valley zebu while it was lowest with Hallikar among the South Indian cattle. Global F statistics showed 6.5% differences among all the investigated zebu cattle breeds and 1.9% differences among Sri Lankan zebu breeds. The Sri Lankan zebu cattle breeds showed strong genetic relationships with Hallikar cattle, an ancient breed considered to be ancestor for most Mysore type draught cattle breeds of South India. Genetic admixture analysis revealed high levels of breed purity in Lanka White cattle with >97% zebu ancestry while significant taurine admixture was observed in Batu Harak and Thawalam cattle. Two major zebu haplogroups, I1 and I2 were observed in Sri Lankan zebu with the former predominating the later in all the three breeds. A total of 112 haplotypes were observed in the studied breeds, of which 50 haplotypes were found in Sri Lankan zebu cattle. Mismatch analysis revealed unimodal distribution in all the three breeds indicating population expansion. The sum of squared deviations (SSD) and raggedness index were non-significant in both the lineages of all the three breeds except for I1 lineage of Thawalam cattle (P<0.01) and I2 lineage of Batu Harak cattle (P<0.05). The results of neutrality tests revealed negative Tajimas D values for both the lineages of Batu Harak (P>0.05) and White cattle (P>0.05) indicating an excess of low frequency polymorphisms and demographic expansion. Genetic dilution of native zebu cattle germplasm is a cause for concern and it is imperative that national breeding organizations consider establishing conservation units for the three native cattle breeds to maintain breed purity and initiate genetic improvement programs.

genetics↗

bioRxiv2020

Age-Stage, Two-Sex Life Table of the Menochilus sexmaculatus (Coccinellidae: Coleoptera) Feeding on Different Aphid Species

Ladybird beetle, Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae), is biological control agent that predate the different aphid species. Both adults and larval stage of M. sexmaculatus feed on aphid species. In this experiment Life table and predation data were collected for M. sexmaculatus feed on four different aphid species Lipaphis erysimi, Myzus persicae, Aphis nerii and Diuraphis noxia. This experiment was conducted under laboratory conditions at 25{+/-}2{degrees}C, 60{+/-}5% RH and L14: D10 h. Different numbers of aphid were provided as a pray in petri dish. The pre-adult development duration of M. sexmaculatus was maximum when fed on M. persicae (12.18 d) and minimum on D. noxia (10.64 d). Similarly, male and female duration was maximum on M. persicae (26.7 d), minimum on L. erysimi (23.67 d) in male and in female maximum on D. noxia (28.00 d), minimum on A. nerii (24.33 d). Net reproductive rate (Ro) range from 117.9 on L. erysimi to 99.55 on M. persicae and intrinsic rate of increase (r) range was 0.21197 d-1 on A. nerii to 0.021559 d-1 on D. noxia. The finite rate of increase ({lambda}) range was 1.240592 d-1 on D. noxia to 1.204918 d-1 on M. persicae, the mean of generation (T) range was 24.68 d-1 on M. persicae to 22.476 d-1 on A. nerii, similarly, the gross reproductive rate (GRR) range was 172.2 d-1 on D. noxia to 115.02 d-1 on M. persicae and Fecundity (F) eggs per female range was 316.8 on D. noxia to 199.1 on M. persicae. In present Study, age-stage two-sex life table gives complete understanding of predator biological aspects against different aphid species. This study will help us to improve mass rearing and use of M. sexmaculatus in biological control of aphids.

zoology↗

bioRxiv2019

Serostatus Testing & Dengue Vaccine Cost-Benefit Thresholds

The World Health Organisation currently recommends pre-screening for past infection prior to administration of the only licensed dengue vaccine, CYD-TDV. Using a bounding analysis, we show that despite additional testing costs, this approach can improve the economic viability of CYD-TDV: effective testing reduces unnecessary vaccination costs while increasing the health benefit for vaccine recipients. When testing is cheap enough, those trends outweigh additional screening costs and make test-then-vaccinate strategies net-beneficial in many settings.\n\nWe derived these results using a general approach for determining price thresholds for testing and vaccination, as well as indicating optimal start and end ages of routine test-then-vaccinate programs. This approach only requires age-specific seroprevalence and a cost estimate for second infections. We demonstrate this approach across settings commonly used to evaluate CYD-TDV economics, and highlight implications of our simple model for more detailed studies. We found trends showing test-then-vaccinate strategies are generally more beneficial starting at younger ages, and that in some settings multiple years of testing can be more beneficial than only testing once, despite increased investment in testing.

epidemiology↗