Anopheles minimus

Anopheles minimus

Range

The Anopheles minimus complex includes A. minumus sensu stricto (formerly A. minimus A), which is located from northern India eastwards through Vietnam and northward across southern China, including Taiwan. Anopheles minumus sensu stricto is one of the main malaria vectors in the mainland of Southeast Asia.

Habitats

Larvae are generally found in small to moderate-sized streams or canals with slow running, clear and cool water, partially shaded and with grassy margins where females prefer to lay their eggs. They develop in various pools (rock, ground, stream and seepage). Unusual larval habitats for An. minimus (e.g. rain water tanks) have also been reported in the suburbs of Hanoi, Vietnam. Anopheles minimus s.l. is commonly found at elevations ranging from 200m to 900m but is rare at altitudes above 1500m. In northern Vietnam and western Thailand, An. minimus occupies a greater variety of habitats, ranging from dense canopy forest to open agricultural fields, particularly traditional rice agro-ecosystems. Anopheles harrisoni has a narrower habitat preference, being more closely linked to recently altered agro-ecosystems (e.g. maize cultivation) in deforested areas.

Resting and feeding preferences

The adult behaviour of An. minimus s.l. is reported as highly diverse for two main reasons: (1) most studies do not differentiate An. minimus and An. harrisoni and (2) these two species are highly opportunistic in their habits, exhibiting considerable behavioural and ecological plasticity. Females of An. minimus mainly bite humans (up to 93% in Assam, India), but the degree of anthropophily/zoophily depends on the availability of alternative hosts (e.g. cattle). This species is mainly endophagic in India, Thailand and central Vietnam, and more exophagic in Cambodia and northern Vietnam. Studies showed that housing in central Vietnam, made with incomplete walls of split bamboo and very large eaves, allows easy entry of the mosquito which would otherwise show exophagic behaviour. Its resting behaviour is reported as exophilic in southern China, Thailand and Vietnam, and mainly endophilic in India. However, the degree of endophagy and endophily of An. minimus is also largely influenced by the use of indoor residual spraying, provoking either a modified behavioural response or a drastic reduction in population density. In contrast, the few studies conducted on An. harrisoni have shown a greater tendency for exophagy, exophily and zoophily. Anopheles harrisoni exhibits two peaks of biting activity in western Thailand, the first in the early evening, between 18:00 and 21:00, with a second, smaller peak from midnight to 02:00 or from 03:00 to 06:00. The early evening peak (before 22:00) has also been observed in northern Vietnam. Anopheles minimus tends to bite later, with peak activity occurring around 22:00 in Cambodia and Thailand, after 22:00 in Vietnam and between 01:00- 04:00 in Assam, India.

Vectorial capacity

An. minimus and An. harrisoni, are vectors of malaria parasites throughout their respective distributions, although further investigation needs to be conducted on An. harrisoni as its role in malaria transmission appears weaker than that of An. minimus, despite it being reported as a main vector in China. An. minimus s.l. is considered a primary malaria vector in the hilly forested regions of mainland Southeast Asia.

This text was modified from Sinka ME et al. (2011) The dominant Anopheles vectors of human malaria in Asia-Pacific: occurrence data, distribution maps and bionomic précis Parasites & Vectors 4:89.

Strains, genome assemblies and gene sets