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 Culex quinquefasciatus, a vector mosquito responsible for transmitting human diseases. Source: www.arbovirus.health.nsw.gov.au
Emerging Infectious Diseases (EIDs) has become an issue of serious concern due to the appearance of pathogens like Human Immunodeficiency Virus (HIV) and Ebola virus; Severe Acute Respiratory Syndrome (SARS) virus; emergence of drug resistant pathogen and outbreak of infectious diseases over large geographic area. The main drivers of outbreak of infectious diseases are growth in human population, consumption pattern and waste generation, which invite human migration, urbanization, poverty, modern agricultural practices, deforestation, and other land use change. In addition, dust transportation, indiscriminate use of antibiotics, modern transportation system for human and animals, wildlife trade ,road building, construction of dam etc. are known to influence emerging infection .The common factor behind such infection is, however, abrupt social and ecological changes.
The remarkable difference in disease outbreak pattern between today and antiquity is the speed, scale, and global dimension of transmission. Rapid evolution of microbes has resulted in the emergence of many new pathogens. On the other hand, malnutrition due to poverty in a large portion of human population has resulted in increased susceptibility to infection.
About three-fourths of recognized EIDs were or are zoonotic, i.e. transmitted between animals and humans. About 15 percent of the 250 EIDs are associated with forests. EIDs like HIV and dengue broke free from their sylvatic cycle in the past and now exist in human-human transmission or a human-vector-human cycle independent of forests. Other EIDs are tuberculosis, hepatitisA, B, C, E, G, most sexually transmitted diseases, opportunistic infection of immunocompromised individuals and a growing number of infections with drug resistant bacteria. Incidence of Nipah virus in Malaysia and cryptosporidiosis in Europe and North America are linked with the modern agricultural practices. Indirect role of road building activity, in the early emergence of HIV types I and 2, is also recognized.
Smallpox is believed to be originated in tropical Asia in association with animal husbandry and forest clearance. Crowding and mixing of people with domestic animals and wildlife in warm humid climate provides opportunity for pathogen evolution, survival and transmission. Forest associated EIDs include viral (yellow fever, dengue, chikungunya, oropucha, SIV, Ebola, Nipah, SARS, rabies, Rocky Mountain spotted fever), protozoan (malaria, leishmaniasis, sleeping sickness) and bacterial (Lyme disease, leptosporiasis) diseases
The first outbreak of yellow fever in Kenya (1992& 1993) reported in forest going people. Dengue, originating from a sylvatic cycle, now infects 50 to 100 million people annually.
Malaria death has calculated to be 300 million to 500 million and its incidence has now increased in some areas of Africa, South America, and South-east Asia which is linked with deforestation and road building.
Many Ebola outbreaks have occurred in forest fringe areas, where human population comes into contact with pathogen through more frequent contact with wildlife.
Interdisciplinary research involving microbiologists, wildlife experts, conservation biologists, ecologists, social scientists, and policy makers would have tremendous relevance in combating the EIDs.
Source: http://www.fao.org/docrep/009/a0789e/a0789e03.htm
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