The impact of variations in temperature on early Plasmodium falciparum development in Anopheles stephensi

Abstract

The effect of temperature on early Plasmodium falciparum development was examined in Anopheles stephensi. The rates of both ookinete development and bloodmeal digestion were lengthened as temperatures decreased from 27 to 21 degrees C. However, low temperatures (21-27 degrees C) did not significantly influence infection rates or densities of either ookinetes or oocytes. In contrast, high temperatures (30 and 32 degrees C) significantly impacted parasite densities and infection rates by interfering with developmental processes occurring between parasite fertilization and ookinete formation, especially during zygote and early ookinete maturation. This study demonstrates clearly that temperature affects the sporogonic development of P. falciparum in anophelines by altering the kinetics of ookinete maturation. These studies not only confirm the ookinete as the key development stage affecting the probability of vector infectivity, they provide new insights into the epidemiology of P. falciparum infections.

Malaria parasite burden and treatment seeking behavior in ethnic communities of Assam, Northeastern India

“…The preponderance of P. falciparum cases during the wet season could be attributed to favorable critical temperatures essential for development of the parasite in the vector host. 13 During this period, transmission of P. falciparum malaria appeared more intense than that of P. vivax as shown by the comparatively high inoculation rates reported in P. falciparum predominant districts. 6 Similar seasonality of malaria parasite species has been documented in other tropical rain forest ecotypes with different vector species, 8,14 but in the present study there were no indications of replacement of P. vivax by P. falciparum.…”

Rethinking vector immunology: the role of environmental temperature in shaping resistance

“…This has been studied for malaria parasites of rodents 26,48 , birds 28–30 , lizards 49 and humans 25,50,51 ; West Nile virus 20 ; dengue virus 19 ; and yellow fever virus 21 . In general, most of these studies show that warming temperatures are associated with a reduction in the development time of the parasite or pathogen.…”

Delayed mortality effects cut the malaria transmission potential of insecticide-resistant mosquitoes

“…This is because only mosquitoes that survive at least 9 further days after consuming infected blood [i.e., the minimum time required for the parasite to complete its extrinsic incubation period (18)] are capable of onward transmission. Malaria vector survival rates are typically low in natural populations, with <20% expected to survive long enough to transmit (16,19). Consequently, even if insecticides have no immediate impact on IR vectors, they could still have a considerable impact on malaria transmission if they reduce the long-term survival of vectors.…”