Chapter 4: Vector and Rodent Related Diseases

Mosquito-borne diseases, especially malaria, dengue and arboviral encephalitis, cause significant concern after disasters with which heavy rains and flooding are associated. The immediate effect is, however, the probable destruction of larval habitats and some accompanying reduction of the vector population with the secondary creation of new larval habitats. It is difficult to determine the probability that greater adult densities will be produced in these habitats and, subsequently, whether an increase in disease transmission will occur.

Such vector related diseases as endemic typhus and certain rickettsial diseases, should cause concern when they are already endemic in or near a disaster area. In addition, fly, cockroach, bedbug, human louse and rodent infestations may pose problems. Immediately after a natural disaster, the fly and rodent densities may appear to be greater, either because they become more visible or have indeed rapidly increased. This is partly due to disruption of sanitary services, such as garbage collection and disposal, and also because increased human crowding is accompanied by increases in the densities of populations of rodents and other vermin which seek the same sources of food and accommodation.

In some regions of the world, unsanitary and crowded temporary shelters and inadequate facilities for storing food provide ideal habitats for bedbugs, lice, fleas, mites, mosquitoes and rodents. Under conditions of this sort, the possibility of transmission of diseases such as louse-borne epidemic typhus, plague and malaria is enhanced.

The potential for increase of vector-borne disease occurrence and related problems during a postdisaster period is summarized on the next page. The immediate period is one to seven days after impact. The "delayed" effects refer to those that occur during the next 30 days or more.

The following sections will cover the issues of identification, evaluation and control of specific problems. The reader interested in routine control operations related to specific diseases, should consult the bibliography.