Anopheline

Malaria. An infectious disease endemic in parts of Africa, Asia, Turkey, the West Indies, Central and South America, and Oceania, caused by protozoa of the genus Plasmodium, and usually transmitted by the bites of infected anopheline mosquitoes. It is characterized by prostration associated with paroxysms of high fever, shaking chills, sweating, anemia, and splenomegaly, which may lead to death. 

Many observations on the effects of DDT-oil aerosols dispersed from the ground as a means for controlling salt-marsh and anopheline mosquitoes have been summarized by La Mer et al. (50). The effects of particle size meteorological conditions, various emulsions, time of exposure, and the relationship of the habits of various mosquitoes to the use of thermal generators are given. This report discusses experiments of a pioneer nature. 

An anopheline mosquito inoculates plasmodium sporozoites to initiate human infection (Figure 52-1). Circulating sporozoites rapidly invade liver cells, and exoerythrocytic stage tissue schizonts mature in the liver. Merozoites are subsequently released from the liver and invade erythrocytes. Only erythrocytic parasites cause clinical illness. Repeated cycles of infection can lead to the infection of many erythrocytes and serious disease. Sexual stage gametocytes also develop in erythrocytes before being taken up by mosquitoes, where they develop into infective sporozoites. 

India also used the pesticide to great effect. When India started its malaria-control program in 1953, almost the entire country was malarial, except for the mountainous areas, and there were, and still are, six different species of Anopheline mosquito vectors. Using DDT, India managed to bring the number of cases down from an estimated 75 million in 1951 to around 50,000 in 1961 and to reduce the annual mortality from malaria from about 800,000 to a few thousand. The achievement of reducing the number of infections to this degree cannot be overstated. India s success persists today because the country continues to use DDT. Reductions in malaria in many other countries were short-lived when they discontinued its use. 

Malaria, transmitted by 18 anopheline mosquito species, continues to be a serious health problem in a number of countries, especially Afghanistan, Iraq, Somalia, Sudan and Yemen an estimated 96% of Eastern Mediterranean malaria cases occur in these five countries. Overall an estimated 60% of the population of the Region are at risk of malaria. 

So far, no serious resistance against pyrethroids has been recorded in vectors or pest populations, although there is an indication that it may be developing in some species. At present, 14 anopheline malaria vector species have developed resistance to organochlorine insecticides, eight to organophosphorus compounds and three to carbamates, and three species have reduced susceptibility to permethrin. 

The sexual cycle (sporogony) takes place in the female anopheline mosquito, while the asexual cycle (schizogony) takes place in humans. 

Insects were the first major focus of pest control, whether to prevent the destruction of food or fiber crops or to limit the spread of insect vectors of disease. There is little doubt that the use of insecticides had a profound impact on the further development of civilization. The control of anopheline mosquitoes and malarial infection, as well as vectors for typhus. 

Malaria is caused by several species of Plasmodium parasites which enter the human bloodstream after penetration of the skin by anopheline mosquitos. Nishina et al. have reported 270 MHz Wand lactate concentration measurements on the blood sera from 20 Nigerians seropositive to Plasmodium, 13 seronegative Nigerians and six healthy Japanese controls. Significantly lower W values and high lactate concentrations were reported for the sera of the malaria-positive group than for the other two groups. 

Ito, J., Ghosh, A., Moreira, L. A., Wimmer, E. A., and Jacobs-Lorena, M. (2002). Transgenic anopheline mosquitoes impaired in transmission of a malaria parasite. Nature 417, 452-455. 

A variety of factors have contributed to the resurgence of malaria, and continue to foster the disease (47). These include socioeconomic and political problems, as well as inadequacies in public health care. Two principal causes of malarial resurgence were (i) the emergence of insecticide-resistant strains of the anopheline mosquitos which are the vectors for transmission of the disease, and (ii) drug-resistant strains of the parasite responsible for the pathology of the most lethal form of the disease, Plasmodium falciparum. Due to the latter, P. falciparum strains which are resistant to the antimalarial effect of chloroquine are spread throughout most of the areas where the disease is endemic, and resistance to more recently introduced antimalarial... 

The variety of malaria parasites is almost as confusing as their nomenclature since the first observation of the living parasite by Laveran in 1880, there have been described over 100 different types, and the number of anopheline vectors is of the same order. Fortunately, only four plasmodial species infect man, namely Plasmodium falciparum, P. malariae, P. ovale and P. vivax, but numerous others parasitise various species of mammals. 

Medica, D.L. and Sinnis, P. (2005) Quantitative dynamics of Plasmodium yoelii sporozoite transmission by infected anopheline mosquitoes. Infect. Immun. 73, 4363 369. 

Female Anopheles gambiae at a blood meal (their male counterparts feed on plant nectar). Besides Anopheles funestus, this malaria vector belongs to the most prominent in Afrika. There are around 460 anopheline species. Many of them feed on blood from animals (zoophilic), e.g. birds, mice and cattle, some 30-40 of them (anthropophilic) prefer however human blood and thereby transfer malaria. 

Towards the end of World War 11, DDT was employed in the South Pacific to contain the spread of malaria. The US Air Force sprayed aerially many islands extensively with 220-280g of DDT per hectare. In Italy, the inner walls of entire houses were treated with up to 2g of DDT per square metre in order to ensure that the contact poison was lethal to anopheline mosquitoes, when they rested after a blood meal on such walls. The procedure had to be repeated twice a year for three to four years (Fig. 5.184). 

DDT-resistant anophelines were observed as early as 1947 in Italy." In Florida, the use of DDT as a larvicide against the salt marsh mosquitoes Aedes sollicitans and Aedes taeniorhynchus began on a small scale in 1943 and within a few years DDT was in extensive use. By 1948, only 5 years after its introduction, the target mosquito species had developed high levels of DDT resistance" and resistance grew even faster in houseflies." ... 

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