Environment Safety

MALARIA

Malaria is still considered the most important parasitic disease affecting man as it is responsible for 1.5 to 2.7 million deaths annually (Belizario and Macatangay, 2004). The vector involved in this disease is the female mosquito of genus Anopheles which transmits the group of parasites that belong to the genus Plasmodium. Four most important species are P. falciparum, P. vivax, P. ovale and P. malariae; the first two are the most common cause of human malaria. The principal malarial vector in the Philippines is Anopheles minimus var. flavirostris which is a night biting mosquito that prefers to breed in slow flowing, partly shaded streams present in foothill areas. It can also adapt to new habitats like irrigation ditches, rice fields and pools. Anopheles litoralis on the other hand is mainly responsible for transmission in coastal areas in Mindanao, particularly Sulu. In streams that have a good exposure to sunlight, Anopheles maculates may coexist with A. flavirostris. Anopheles mangyanus has similar breeding places and seasonal prevalence as A. flavirostris but are more common in forest fringes.

Vector Bionomics Resting habits  It rests during daytime in human dwellings and cattlesheds Breeding Places  breeds in rainwater pools and puddles, borrowpits, river bed pools, irrigation channels, seepages, rice fields, wells, pond margins, sluggish streams with sandy margins.  extensive breeding is generally encountered following monsoon rains Biting time  biting time of each vector species is determined by its generic character, but can be readily influenced by environmental conditions.  most of the vectors, including Anopheles culicifacies, start biting soon after dusk.  Peak transmission occurs at the beginning and at the end of the rainy season. Life Cycle of Malaria Parasite 1. Sporozoites (infective stage) in salivary gland 2. Oocysts in stomach wall 3. Male and female gametocytes. 4. Liver phase 5. Release of merozoites from liver 6. There...