Public Health Vectors and Pests

 In epidemiology, a vector is an organism that does not cause disease itself but which transmits infection by conveying pathogens from one host to another. There are two types of vector that convey infectious organisms to a host: mechanical and biological. Microbes do not multiply within mechanical vectors - mechanical vectors only physically transport microbes from host to host. In contrast, microbes must propagate within a biological vector before the biological vector can transmit the microbes.

The transmission of vector-borne diseases to humans depends on three different factors: the pathologic agent; the arthropod vector; and the human host.

The majority of vector-borne diseases survive in nature by utilising animals as their vertebrate hosts (zoonoses). For a small number of zoonoses, such as malaria (and dengue fever), humans are the major host, with no significant animal reservoirs. Intermediary animal hosts often serve as a reservoir for the pathogens until susceptible human populations are exposed.
Key components that determine the occurrence of vector-born
e diseases are: (i) the availability of vectors and intermediate and reservoir hosts; (ii) the prevalence of disease-causing pathogens suitably adapted to the vectors and the human or animal host; (iii) the local environmental conditions, especially temperature and humidity; and (iv) the susceptibility of the host.

Although this disk concentrates primarily on the vectors of disease, it also covers some pests of public health interest.
A pest is an organism which has characteristics that are can be injurious or unwanted. They can it cause damage to agriculture through feeding on crops or being parasites on livestock, such as codling moth on apples, or boll weevil on cotton. An animal can also be a pest when it causes damage to a wild ecosystem or carries germs within human habitats. Examples of these include those organisms which vector human disease, such as rats and fleas which carry the plague, or mosquitoes which vector malaria.

It is almost safe to presume that people will always have to live with vector-borne diseases, and that it would be folly to try to eradicate vectors and pests as some of them are beneficial to humans and the environment. Time has also shown that maintaining a strong public health infrastructure and undertaking research activities directed at improved means of control, —possibly utilizing biological and genetic-based strategies, combined with the development of new or improved vaccines for diseases such as malaria, dengue and Lyme disease—should lessen the threat to human health.

This project was undertaken by the following:

  • Mr M Kgware : Durban University of Technology
  • Mr J Maniram : Environmental Health Component, KwaZulu-Natal Department of Health
  • Mr PP Maharaj : CDC, eThekwini Municipality
The knowledge gained would not have been possible had it not been for the magnanimous financial contribution made by the Danish Government to whom we owe a sincere gratitude.


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