RESISTANCE OF EARLY MIDGUT STAGES OF NATURAL PLASMODIUM FALCIPARUM PARASITES TO HIGH TEMPERATURES IN EXPERIMENTALLY INFECTED ANOPHELES GAMBIAE (DIPTERA: CULICIDAE)

• Published in: The Journal of parasitology 2004-08, Vol.90 (4), p.764-768
• Main Authors: Okech, Bernard A, Gouagna, Louis C, Kabiru, Ephantus W, Walczak, Elizabeth, Beier, John C, Yan, Guiyun, Githure, John I
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Animals; Anopheles - metabolism; Anopheles - parasitology; Anopheles gambiae; Aquatic insects; Biological and medical sciences; biological development; Blood; Carrier State - parasitology; Carrier State - transmission; Child; Child, Preschool; Culicidae; Disease transmission; Dissection; Dry season; Enumeration; Female; Fundamental and applied biological sciences. Psychology; Gametocytes; General aspects; General aspects and techniques. Study of several systematic groups. Models; Heat resistance; heat stress; High temperature; High temperature effects; Hot Temperature; Humans; Infections; Informed consent; insect vectors; INVERTEBRATE-PARASITE RELATIONSHIPS; Invertebrates; Invertibrate-Parasite Relationship; Kenya; macrogametocytes; Malaria; Malaria, Falciparum - parasitology; Malaria, Falciparum - transmission; Midgut; Mortality; Mosquitoes; Mosquitos; Oocysts; Ookinetes; Parasite resistance; Parasites; pathogen survival; Plasmodium falciparum; Plasmodium falciparum - growth & development; Plasmodium falciparum - physiology; sporogony; temperature; Tropical Climate; Tropical environment; Tropical environments; Vector-borne diseases; Zygotes
• ISSN: 0022-3395; 1937-2345
• DOI: 10.1645/GE-135R1

We studied the effects of high temperature, 30 and 32 versus 27 C on early Plasmodium falciparum development in Anopheles gambiae experimentally infected with gametocytes from 30 volunteers with mean density of 264.1 gametocytes/μl blood (range: 16–1,536/μl). From several batches of mosquitoes, fed by membrane feeding, midguts of individual mosquitoes were dissected at 24 hr for ookinete enumeration and at 7 days to quantify oocysts. There were temperature-related differences in mean ookinete intensity per mosquito midgut, with 9.71 ± 1.6 at 27 C, 9.85 ± 2.32 at 30 C, and 3.89 ± 0.81 at 32 C. The prevalence of oocyst infection decreased with an increase in temperatures from 15.9 to 8.5 to 6.4% at 27, 30, and 32 C, respectively. The average oocyst intensities for the infected mosquitoes increased with temperatures from 2.9 at 27 C to 3.5 at 30 C, and to 3.3 at 32 C. However, the success of infections was reduced at 30 and 32 C, and resulted in greater losses during consecutive inter-stage parasite development. The most significant impact of high temperatures occurred at the transition between macrogametocytes and ookinetes, whereas the transition between ookinetes and oocysts apparently was not affected. In contrast to other reports, exposure of mosquitoes infected with natural parasites to high temperatures did not eliminate preoocyst stages, as has been observed from laboratory studies using the NF-54 strain of P. falciparum. This observation of parasite resistance to high temperatures is consistent with the natural situation in tropical environments where perennial malaria transmission occurs during hot dry seasons.