Arthropods transmitting diseases

The use of personal protective measures, such as topical insect repellents, has been essential in the prevention of arthropod transmitted disease. However, skin irritation is a frequent side effect of repellents in soldiers (Fai and Lee 1996). Some studies reported on the development of severe bullous irritant dermatitis from use of the repellent diethyl toluamide (Lamberg and Mubrennan 1969 Reuveni and Yaqupsky 1982 Amichai et al. 1994). 

There have been several reviews concerning the safety of deet -" and they have attested to its generally acceptable safety profile in normal use, supporting the recommendation that it is the repellent of choice when visiting areas of endemic arthropod-borne diseases, particularly those transmitted by mosquitoes. 

There is a vast range of arboviral diseases transmitted by mosquitoes, and a few of those that are important to the travelers or in areas outside the tropics are presented in Table 13.4 along with a short discussion. Many of these also occur where other arthropod-borne diseases are present so that a repellent would usually be necessary. 

Arthropod parasites and the diseases they transmit are among the most important deterrents to the progress of tropical agriculture in Africa and Central and South America. No general agricultural economy can be entirely successful if domestic animals and poultry are excluded or their husbandry for any reason is unprofitable. In many tropical areas the entire livelihood of families or tribes depends on cattle that are used for food, draft, and as a measure of wealth. Outbreaks of parasites or disease epizootics that decimate or debilitate their animals can mean financial disaster or even famine for these people. 

Insects, spiders, scorpions, crabs, centipedes, millipedes, and even some plankton are arthropods, the largest and most diverse animal phylum. Some are capable of producing very powerful toxins as an aid in the quest for food. Humans come in contact with these toxins, usually by accident or as a result of the animal defending itself. Some insects, mosquitoes and ticks for example, are capable of transmitting other organisms to humans that cause disease. While these organisms may be toxic to humans, they are not toxins and will not be discussed in this chapter. 

The virus was not, however, isolated until 1928, and a vaccine was first developed by the South African Max Theiler in 1939. Early attempts to eradicate the mosquito by physical means, and later through the use of insecticides like DDT, were only partially successful, and the disease is still endemic in much of West Africa and in South America, but not, surpisingly, in Asia. It has been suggested that this may be due to the fact that it closely resembles the virus that causes dengue fever, which is endemic in all of Asia. They are both arboviruses, which stands for arthropod-borne viruses, are both transmitted via the bite of a mosquito and cause a haemorrhagic illness. Survivors of dengue fever would be expected to have partial immunity (at least) to yellow fever. 

A carrier, usually an insect or other arthropod, that transmits the causative organisms of disease from infected to non infected individuals, especially one in which the organism goes through one or more stages in its life-cycle. 

TYPHUS. A group of infectious and contagious diseases caused by the Rickettsia genus of bacteria and transmitted by arthropods, such as fleas. 

---