Version française

Malaria N 9 - Subject N 5


ANOPHELES - PLASMODIUM - RELATIONSHIPS; CONSEQUENCE FOR THE MALARIA TRANSMISSION
V. Robert


SUMMARY
The inter-relationship between Anopheles and its vectors constitute a subset of relationships which link together the three malaria actors: Man, Plasmodium, and Anopheles. The transmission of malaria involves as much the transfer of the parasite from mosquito to man as from man to mosquito. The following will be discussed in succession, with the aim of illustrating a few particular points of the Anopheles-Plasmodium relationship and their impact on the transmission of malaria: the infected bite of on anopheles, factors modulating the infectivity of gametocytes in the case of for the vector and finally transmission relationships between transmission-morbidity-mortality.

The bite of an anopheles, carrying sporozoites within its salivary glands, involves three distinct but linked processes which are at the some time both distinct and related: the penetration and probing by the mouth parts into the skin of the buccal appendages (probing), the injection of saliva containing sporozoites and blood feeding. Recent discoveries, concerning this infected bite focus mainly on the following four points:

Factors modulating gametocyte infectivity for the vector are multiple and once again up to now, relatively poorly understood. Six factors are described here:

Transmission-morbidity-mortality relationships lie at the heart of the anti-anopheline control problematic. In an epidemic or Lower poor endemicity area it has been clearly shown that transmission must be the lowest possible. On the other hand, in areas of mid to high endemicity, the comparison of epidemiological situations, varying according to the level of transmission, provide solid arguments to show that the level of transmission level is not a determinant factor for overall malaria morbidity and malarial mortality overall. However, this transmission level is a determinant factor for the dynamics of immune acquisition morbidity and mortality: in area of high endemicity the youngest age groups are those which show the highest morbidity and mortality rates clearly more affected in areas of high transmission, whilst the consequences of malaria are distributed more equitably between the different age groups in the weaker transmission regions. Many anti-vector projects (for example with bednets impregnated with insecticide) have shown some efficacy and an improvement in the malaria situation, but it is likely that:


Contents N9Previous subjectOrder
this article
Next subjectNext contents
Pages maintained by Dr. Stéphane DUPARC - October 98