Middle East DVEP - Armed Forces Pest Management Board

personnel moving into an endemic area from one that is free from filariasis may developsymptoms such as swelling of the lymph glands, headache and fever many months beforelarvae become mature. American military forces in the Samoan-Ellice-Wallis Islandsfrom 1942 to 1944 rapidly developed swollen lymph glands and extremities followingrepeated exposure to infected mosquitoes. Acute filariasis is the primary militaryconcern, because its symptons develop fairly rapidly and may be severe enough to causeremoval of troops from their duties. In addition, observing local members of thepopulation with grotesque deformities caused by chronic infection can have an adversepsychological impact. Medical personnel should be aware that troops with brief exposureto infection are often not diagnosed until after they return from deployments.Disease Distribution. Wuchereria bancrofti occurs in most tropical and somesubtropical regions in Latin America, Africa, Asia and the Pacific islands. Massmigrations of infected humans are usually required to introduce the disease to new areas.In the Middle East, sporadic cases have been reported from Iran, Oman, Yemen andsouthwestern Saudi Arabia (Figure 13). Seasonal distribution generally coincides withrainy periods in endemic areas. Transmission in the principal foci in Yemen andsouthwestern Saudi Arabia is from April to August.Transmission Cycle(s). Microfilariae circulating in human blood are ingested bymosquitoes and undergo several days of development before the vector can transmitinfective stages of the nematode. Infective parasites enter the bloodstream directlyduring a mosquito bite. A few nematode larvae are deposited on the skin and can enterthe host through skin abrasions. In humans, larvae undergo development to adultsthat produce microfilariae for many years. Over most of its geographic range, includingthe Middle East, W. bancrofti microfilariae usually exhibit pronounced nocturnalperiodicity and consequently are ingested by night-biting mosquitoes. Peak abundance ofmicrofilariae in the blood occurs between 2300 and 0300 hours. Culex pipiensquinquefasciatus is the most common urban vector. In rural areas, transmission ismaintained mainly by Anopheles spp. There are no known animal reservoirs ofBancroftian filariasis.Vector Ecology Profiles.Members of the Culex pipiens complex are the primary vectors. This complex includesCx. p. pipiens, Cx. p. molestus, Cx. p. fatigans, and Cx. p. quinquefasciatus. Culexbitaeniorhynchus, Aedes aegypti, and Anopheles arabiensis are considered possiblesecondary vectors. The Cx. pipiens complex is widely distributed throughout the region.Aedes aegypti is also widely distributed. Other vectors, including Cx. bitaeniorhynchusand An. arabiensis, have limited distributions in the Middle East. Culexbitaeniorhynchus is found only in Iran, and An. arabiensis is reported only from Yemenand southwestern Saudi Arabia. The distribution of mosquitoes reported from the MiddleEast is presented in Appendix A.1.125