Chain Transmission of Filariasis
Filariasis transmission can occur when there are three elements, namely:
1. A source of transmission, is human or host reservoir containing the microfilariae in the blood.
2. The existence of a vector, is mosquitoes that can transmit filariasis.
3. Humans are susceptible to filariasis.
Someone can be infected with filariasis, where a person gets a bite of infective mosquitoes, the mosquitoes containing infective larvae (larval stage 3 - L3). At the time of infective mosquito bites humans, the L3 larvae will exit from the proboscis and live in the skin surrounding the hole mosquitoes. At attract mosquitoes proboscis, L3 larvae will go through a mosquito bite wounds and move toward the lymph system. In contrast to the transmission of malaria and dengue, see the cause of filariasis transmission chain is not easily transmitted from one person to another in a particular area, so it can be said that a person can be infected with filariasis, if he gets a mosquito bite a thousand times.
L3 larvae Brugia malayi and Brugia timori will become adult worms in the period of approximately 3.5 months, while Wuchereria bancrofti takes approximately nine months.
Besides difficult occurrence of mosquito-to-human transmission, real ability to get the microfilariae when mosquitoes suck blood containing the microfilaria is also very limited, the mosquitoes that suck too much microfilaria can experience death, but if microfilariae are sucked too little can minimize the number of microfilariae that L3 larva will be transmitted.
Vector density, temperature and humidity affect the displacement of filariasis. Temperature and humidity affect the life of a mosquito, so that existing microfilaria in mosquito body is not enough time to grow into infective larvae L3 (extrinsic incubation period of parasites). Extrinsic incubation period of Wuchereria bancrofti to between 10 -14 days, while Brugia malayi and Brugia timori between 8 -10 days.
Periodicity of microfilariae and mosquito biting behavior influence infection risk. Microfilariae that are periodically nocturnal (microfilaria only found in the peripheral blood at night) has a vector that actively seek out the blood at night, so that transmission also occurs at night. In regions with sub-periodic microfilariae nocturnal and non-periodic, transmission can occur day and night.
In addition to the above factors, population mobility from filariasis-endemic areas to other areas or vice versa, the potential to become the media of inter-regional spread of filariasis.