Middle East DVEP - Armed Forces Pest Management Board

The risk of transmission is seasonal, occurring during the summer (May to September) inthe more northern countries of Cyprus, Iran, Iraq, Israel, Jordan, Lebanon and Syria. Inmost of Saudi Arabia and Kuwait, risk of infection is year-round, although incidence maybe limited in arid areas. Transmission is greatest during peak rainy periods from Marchto May. In the southwestern part of Saudi Arabia (Asir region), Yemen and Oman,transmission is year-round because of more extensive rainy periods.Transmission Cycle(s). Murine typhus is a zoonotic infection associated with domesticrats (Rattus rattus and R. norvegicus) and vectored by their fleas (Xenopsylla cheopis andLeptopsylla segnis) and the rat louse, Polyplax spinulosa. The Oriental rat flea, X.cheopis, is the most important vector. Neither rodents nor their ectoparasites are affectedby infection with R. typhi. Murine typhus is transmitted by inoculating crushed fleas orinfective flea feces into the skin at the bite site. Scratching due to the irritation of fleabites increases the likelihood of infection. Rickettsia typhi is rarely transmitted directlyby flea bite. Other routes of infection are by inhalation of dry flea feces containingrickettsiae, and ingestion of food contaminated by rodent urine. Dried rickettsiae remaininfective for weeks. Murine typhus is not transmitted from person to person.Vector Ecology Profiles.The primary vector is the Oriental rat flea, X. cheopis. Cat and dog fleas,Ctenocephalides felis and C. canis, as well as the body louse, Pediculus h. humanus, arepotential secondary vectors for humans. However, these vectors have not beenincriminated in epidemics in this region. The northern rat flea, Nosopsyllusfasciatus, the rat louse, Polyplax spinulosa, and the tropical rat mite, Ornithonyssusbacoti, are vectors that maintain the enzootic cycle of the disease.The Oriental rat flea, although distributed throughout the 15 countries of the region, is notas abundant as it is in some other regions of the world. It occurs primarily wherecommensal rodents are found, particularly R. norvegicus. Commensal rodents, as well asthe primary vector, are more widely distributed in urban areas in northern parts of theregion, including Turkey, Syria, Iran, Iraq, Lebanon, and Jordan. In Saudi Arabia,Yemen and Oman, commensal rodents have a more limited coastal distribution, and arelargely confined to urban areas. The zoonotic vectors, including N. fasciatus, O. bacoti,and P. spinulosa, have similar distributions. Appendix A.4. list the distribution of fleasin the Middle East. See plague, page 96, for information on flea biology.Polyplax spinulosa, the spiny rat louse, remains in close association with its rodent hosts.Female lice attach eggs to the hairs of their hosts. Developing stages spend their entirelife cycle on the rodents. Lice are only transferred from rodent to rodent by body contact.These lice feed on the blood of their hosts but do not feed on humans.Ornithonyssus bacoti, the tropical rat mite, lives on commensal and other rodentsthroughout the region and feeds on blood and other fluids that ooze from the tiny bitewounds. Engorged females start laying eggs within 2 days after feeding, and continue tolay groups of eggs for 2 to 3 days. Eggs hatch in 1 to 2 days and develop into larvae,protonymphs, and deutonymphs. The entire life cycle, through the adult stage, requires95