Detection of Chikungunya virus in Aedes aegypti during 2011 outbreak in Al Hodayda, Yemen

In October 2010, the Ministry of Public Health and Population reported an outbreak of dengue-like acute febrile illness in Al Hodayda governorate. By January 2011, a total of 1542 cases had been recorded from 19 of the 26 districts in the governorate with 104 purportedly associated deaths. In response this event, in January 2011 entomological investigations aimed at identifying the primary vector and the epidemic associated etiological agent were carried out. Based on the reported cases and the progress of the outbreak in the governorate, mosquito collection was undertaken in two of the most recent outbreak areas; Al Khokha district (130 km south of Al Hodayda) and Al Muneera district (100 km north). Mosquito adults were collected from houses using BG-sentinel? traps, aspiration of resting mosquitoes and knock-down spraying. Indoor and outdoor containers adjacent to the houses were inspected for larvae. Subsequently mosquito pools were analyzed by RT-PCR for detection of the four dengue virus serotypes (DENV-1, DENV-2, DENV-3, DENV-4), and for Chikungunya virus (CHIKV). Aedes aegypti was the dominant mosquito species collected. Four pools represent 40% of the tested pools, all containing adult female Ae. aegypti, were positive for CHIKV. Three CHIKV isolates were obtained from the RNA positive mosquito pools and identified by rRT-PCR. This finding marks the first record of CHIKV isolated from Ae. aegypti in Yemen. The larval container and Breteau indices in the visited localities surveyed were estimated at 53.8 and 100, respectively. The emergence of this unprecedented CHIKV epidemic in Al Hodayda is adding up another arboviral burden to the already existing vector-borne diseases. Considering the governorate as one focal port in the Red Sea region, the spread of the disease to other areas in Yemen and in neighboring countries is anticipated. Public health education and simple measures to detect and prevent mosquito breeding in water storage containers could prevent and reduce the spread of mosquito-borne viruses like CHIKV and DENV in Yemen.