An update on the incidence of dengue gaining strength in Saudi Arabia and current control approaches for its vector mosquito

Physical and cultural strategies for dengue vector control in Saudi Arabia

These strategies for controlling the dengue vector can be partially effective for preliminary elimination of the vector mosquito and primarily include elimination of the possible breeding sites of larvae. However, such efforts are rarely practiced in KSA. Also, public awareness of life cycle of the dengue vector and its favorable domestic and peri-domestic habitats is minimal. Therefore, it is suggested that intensive efforts should be made to enhance public awareness for the overall health promotion of the general public in KSA. Association between larval control strategies and health education of the public should be maintained. The residents should be aware of not only the control activities conducted by the special mosquito control teams but should also seriously respond to the health education-related information dissemination scheduled by the relevant governmental authorities. For dengue control, public awareness and education concerning the breeding sites of the dengue vector mosquito and its physical and cultural control are vital in population management of this container-breeding vector.

Chemical control

Generally, control of dengue vectors in the Middle Eastern region is primitive and in most cases non-existent[7]. In KSA, during the last few decades, several insecticides have been employed intensively for controlling the dengue vector. For example, pyrethroids, such as cyfluthrin, deltamethrin, lambdacyhalothrin, permethrin were reported to be effective chemical controls (adulticidal) agents in KSA[10]. These insecticides are well-known for their quick and efficient knock-down action, this property has made them the most popular chemicals for insect control including mosquitoes[11, 12]; however, frequent and regular use of these insecticides is conducive to the development of resistance in the target insect(s) globally[12].

Based on a municipality report of the city of Makkah, in 2007, the estimated amount of undiluted mosquito adulticides and larvicides used were 17975 and 3899 liters, respectively[13]. In early 2006, the KSA government substantially increased mosquito control budget to prevent the spread of dengue in Jeddah; the estimated budget amounted to seven billion Saudi Riyals[10]. However, even with such a high expenditure, no significant decline in the dengue incidence occurred[14] and spatial distribution of Ae. aegypti[8] as well as circulation of the four dengue serotypes[15] persisted. In view of such costly control efforts, it is assumed that this unexpected failure could partially be due to contracting out the mosquito control work to private companies that lacked in terms of precise mosquito control knowledge, use of appropriate science-based strategies, and perhaps efficient professional supervision. It is suggested that public awareness concerning appropriate measures of hygiene and sanitation to eliminate the possible breeding sites of mosquitoes should be organized frequently by respective local municipal and federal Ministry of Health authorities. In addition, mosquito vector control by house-to-house spraying in KSA is still not practiced properly because it is managed by private companies having small teams of mostly untrained or undertrained staff that apply the insecticides without much knowledge and experience of insecticidal application and dealing with insecticides and mosquito population management. In many cases, the control resulting from contracted private companies was inadequate and ineffective. This may have been due to insecticidal under dosing by the contractors to reduce their insecticidal, operational, and management costs. In addition to all of the above-mentioned shortcomings, it has been observed that, the workers sometimes mixed and applied the insecticides merely by themselves without any expert supervision concerning dosage. Consequently, significant negative impact on control effectiveness would be expected. Furthermore, there are some other factors that have some negative bearing on control effectiveness of the dengue vector in KSA. For example, several entrepreneurs in Jeddah were reported to promote adulterated insecticides as a "magic fix" to kill mosquitoes without any awareness of their side effects and long-term adverse impact on human health and possible development of resistance in the target mosquitoes[16]. It would be fitting to emphasize here that field applications of insecticides under contracts are made on a routine basis without any pre- and post-treatment population assessment(s) of prevailing populations of mosquitoes, and thus unnecessarily amplifying insecticidal pollution in the environment as well as risking onset of resistance phenomenon in the target mosquitoes. In Saudi Arabia, infrastructure development and urbanization along with human population growth have been rather rapid during the past 40 years or so. Specifically, the city of Makkah is developing rather rapidly in various sectors without any consideration or planning to curb the spread of dengue vector. Nevertheless, for any dengue-related entomological observations, permission to enter people’s dwellings must be granted by the male head of the family (cultural practice) and is often an impediment in the crucial requirement of mosquito population assessment and dengue control process. Some residents are afraid of police or immigration authorities and therefore entry of mosquito researchers and spray teams into homes for research and control purposes becomes more difficult and this problem is usually overcome by following educational health officers for the relatively easier access to the houses.