Effect of the intensity of Hepatozoon gracilis parasitaemia on some biological aspects of Culex (Culex) pipiens (Diptera: Culicidae)

The bean skinks were collected manually from Abu.Rawash, Giza, Egypt, separated according to size and investigated for H. gracilis infection. Intensity of parasitaemia was determined as slight (≤ 2% per 1000 counted erythrocytes), moderate (3-10% per 1000 counted erythrocytes) and high (11-20% per 1000 counted erythrocytes). Cx. (Cx.) pipiens L were reared under controlled laboratory conditions (20 + 1 °C, 60–70% RH and 10L: 14D photoperiod). Four groups of 3-4-day-old females, 50 individuals each, were starved 12 h prior to feeding. The first group was used to feed on parasite-free bean skink while the other groups were offered blood meals from slightly, moderately and highly infected lizards.  The fully engorged females from each group were transferred separately to oviposition tubes and observed daily for longevity and reproductive capacity. Data were statistically analyzed by ANOVA using SPSS software, Ver., 15.0.
The present study declared that the majority of naturally infected bean skinks were slightly infected. Generally the parasitic infections were costive to their host vector and this cost was manifested as a reduction in reproductive and transmission capacities. Preoviposition period was reduced by 15% and increased by 55% in case of mosquitoes fed on highly and moderately infected skinks, respectively, as compared to control. Fecundity was reduced by 48, 37 and 18% and fertility was reduced by 8, 3 and 6% in case of mosquitoes fed on highly, moderately, slightly infected skinks, respectively, as compared to control. No significant difference in the egg incubation period was observed between control and infected groups. Adult longevity was reduced by 40% in case of mosquitoes fed on highly infected skinks and increased approximately 2 folds in case of mosquitoes fed moderately and highly, infected skinks as compared to control.
The present study suggested a decreased competence of Cx. (Cx.) pipiens in the hepatzoonosis disease circulation in nature when the infection intensity was high or moderate. On the other hand, the vector is a very strong candidate in the disease circulation in nature in case of slight intensity of infection.