Pest and Vector Control

· Insects and rodents carry and spread diseases and can spoil food supplies;

· Physical screens are the best immediate measures;

· Preventive action to eliminate or limit breeding areas and conditions favourable to the vectors is the best long-term solution;

· Specialist supervision of all chemical measures and local knowledge of resistance is necessary;

· Avoid chemical control where possible.

General Considerations

66. The environment in a refugee emergency is typically favourable to the proliferation of disease-carrying insects and rodents ("vectors"), which can also destroy or spoil large quantities of food.

67. Flies tend to breed in areas where food or human excretia are present, mosquitoes where there is stagnant water, and rats where there is food, garbage and cover. As a result of overcrowding and inadequate personal hygiene, lice, fleas, mites, ticks and other arthropods may also cause health problems. Table 2 gives an indication of common vectors and related diseases.

68. Reducing the numbers of flies, mosquitoes and rodents quickly in an emergency is difficult and physical screens may be the best immediate measure. Over the longer term, the most effective method of controlling insects and rodents is preventive: to improve personal hygiene, sanitation, drainage, garbage disposal and food storage and handling practices and thus make the environment less favourable for the vectors. Examples of practical measures are the removal of stagnant waste water, regular garbage collection, use of oil in latrines and provision of soap and sufficient water for washing. The recommended monthly supply of soap is 250 g soap per person per month. The programme should provide for regular inspection and be integrated with other public health measures.

69. The problems should be discussed with the refugees and education given on the significance of vector control. Where solutions unfamiliar to the refugees are employed, these must be carefully explained.

70. Whatever the nature of nuisances and pests, one should avoid having systematic recourse to chemical control by means of pesticides (insecticide, rodenticide, molluscicide, etc.). Such products are costly and toxic to both human beings and the environment. There is a risk of poisoning during transport, storage, handling and of course spraying the chemicals. Also, pests can develop resistance to the chemicals.

Table 2 - Vectors Which May Pose Significant Health Risks

VECTOR	RISKS
Flies	Eye infections (particularly among infants and children), diarrhoeal diseases
Mosquitoes	Malaria, filariasis, dengue, yellow fever, encephalitis
Mites	Scabies, scrub typhus
Lice	Epidemic typhus, relapsing fever
Fleas	Plague (from infected rats), endemic typhus
Ticks	Relapsing fever, spotted fever
Rats	Rat bite fever, leptospirosis, salmonellosis

Physical Control

71. Measures described in this chapter to deal with excretia and waste disposal will also help control pests (flies and rodents particularly).

72. The elimination of stagnant water and other breeding and resting sites for mosquitoes through drainage is important and the drainage network must be maintained.

Chemical Control

73. Obtaining precise information on chemicals which are used or authorized to be used in the country (i.e. registered list of pesticides if any) should be the first priority.

Insecticide spraying carried out on a routine basis must be avoided, and in any event should be consistent with the rules and procedures in force in the host country.

74. Advice from specialists, particularly medical entomologists, should be sought to minimize the risks and to maximize the impact on target-species.

75. Staff assigned to such tasks must be trained on technical aspects, informed about health hazards linked with handling and spraying of pesticides, and protected by means of adequate clothing (mask, boots, gloves, etc.).

76. The use of rodenticides should always be adopted in agreement with medical staff. Rats are favoured carriers of vectors (such as fleas) of bubonic plague and murine typhus. When these diseases may be present it is more important to take measures directly against the vectors themselves - i.e. the fleas, rather than the rats - because destroying the rats will simply cause the fleas to leave the dead bodies of the rats and become more of a threat to people.

77. The body louse is the only proven vector of louse-borne epidemic typhus and relapsing fever. If there is a serious increase in body louse infestation, quick action is required by properly trained personnel. This generally involves dusting individuals' inner clothing and bedding with an insecticide or the use of clothing fumigants. There is widespread resistance in lice to some insecticides and expert local advice must be sought.