University of Khartoum

Biological Studies on Hyalomma anatolicum (Acari: Ixodidae) Fed on Crossbred Calves in Khartoum State, Sudan

Biological Studies on Hyalomma anatolicum (Acari: Ixodidae) Fed on Crossbred Calves in Khartoum State, Sudan

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Title: Biological Studies on Hyalomma anatolicum (Acari: Ixodidae) Fed on Crossbred Calves in Khartoum State, Sudan
Author: Khogali, Rua Khogali Ibrahim
Abstract: This study was conducted to investigate the biology of Hyalomma anatolicum fed on crossbred calves (3 to 6 months old) kept under zero grazing system. The study included feeding periods, drop-off rhythms, developmental periods and survival of unfed stages in field and laboratory in different seasons at Shambat during 2016 and 2017. Using ear bags, the tick stages were placed in the ears of calves, three for each stage. Drop-off rhythms of the engorged ticks were monitored at 2-hours intervals (0700 to 2000 hrs.). To determine the developmental and survival periods, tick stages were kept at the laboratory (27°C and 85% R.H.) and in the field conditions. They were monitored at intervals (three days, weekly, and monthly for larvae, nymphs and adults, respectively). The data obtained were analyzed using SAS (ver. 9.1). Shambat meteorological data were obtained from Meteorological Authority, Ministry of Environment, Natural Resources and Physical Development. Larvae, nymphs and females were fed for two to three days, three to five days and five to 10 days, respectively. All (100%) of the larvae behaved as 3-host ticks. Significantly (P≤ 0.001) high numbers of engorged larvae dropped between 2000 hrs. and 0700 hrs. while significantly (P≤ 0.001) high numbers of engorged nymphs dropped between 1600-2000 hrs. Insignificant numbers of females dropped at 1000 hrs. and 2000 hrs. The developmental periods were significantly (P≤ 0.001) longer in the laboratory than in the field. Pre-oviposition period took a mean of eight days in the laboratory, in the field it was six days, 6.5 days and seven days in July, November and May, respectively. Pre-eclosion period was with means of 21 days and 30 days in the field and laboratory, respectively; the shortest period was in May (18 days) followed by July (22 days) and November (24 days). Hatchability of eggs was 100% in laboratory and field in July and November, but only 43% in May. Significant linear relationship was observed between female engorgement weights and the weights of egg batches laid; the peak of egg laying in the laboratory was on days four and nine. The mean premoulting periods of engorged larvae was 13 days and eight days in laboratory and field, respectively. Seasonally, these periods ranged between means of eight to10, five to nine, nine to10 and seven to eight days in March, May, August and September, respectively. The mean pre-moulting period of engorged nymphs was nine to10 days and 13-15 days in the field and laboratory, respectively; in August, 70% of unfed larvae and nymphs survived for three weeks and 2.5 weeks, respectively; in May 16% of unfed larvae survived for one week while there was no unfed nymphs survive for more than four days. This study of H. anatolicum fed on calves is the first of kind in the Sudan. It concluded that drop-off rhythms of H. anatolicum mostly occurred at night and that the seasons influenced developmental periods with air temperatures being the main factor while humidity had no primary influence. Adults failed to attach and feed in winter. Unfed larvae were more resistant to desiccation than unfed nymphs. The whole life cycle, under field conditions, ranged between seven to 10 weeks with ability to survive nearly 10 weeks. It was recommended to study seasonal prevalence of H. anatolicum in relation to diseases it transmits. Data obtained from this investigation provide basis for control planning strategies of the vectors and diseases.
URI: http://khartoumspace.uofk.edu/123456789/27037


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