Zoonotic and vector-borne diseases pose a profound threat to the human health. They increase the level of morbidity and mortality among humans. Therefore, currently, there is an urgent priority to implement effective methods of controlling the above-mentioned diseases.
Zoonotic and vector-borne pathogens tend to spread rapidly across wide territories. A constant surveillance of animal and bird reservoirs is an effective method of assessment of risks to human health. It helps identify and eradicate infection in animals as well as protect people from contagion. Besides, animal health should be properly controlled and maintained, since such actions will reduces the risk of many zoonotic diseases and prevent the spread of infection. In addition, vaccination is a beneficial method that provides a defense against zoonosis and ensures public health.
Chemical, biological, and genetic controls belong to the methods that prevent vector-borne diseases. Chemical control involves insecticides and repellents that kill insects and protect people from their bites respectively. These are effective methods of self-protection. Biological control is based on utilizing such biological organisms as microbes that cause insect diseases. It does not pollute the environment and may be relatively cheap. Lastly, genetic control aims to modify vectors genetically in order to reduce their birth rate. The sterile-insect technique is the most widely applied approach within genetic control. It presupposes the release of sterile adult males.
Thus, constant surveillance, maintenance of animal’s health, and vaccination represent the current methods of controlling zoonosis and protecting public health. With the aim to control vector-borne diseases, chemical, biological, and genetic methods are effectively applied.
Malaria, dengue fever, and leishmaniasis refer to vector-borne diseases that lead to millions of human deaths annually. These communicable diseases are transmitted to people via the bites of the infected insects called vectors. Certain environmental factors contribute to the distribution of the above-mentioned diseases.
Malaria is a severe infectious disease caused by protozoan parasites of the genus Plasmodium, such as Plasmodium falciparum, Plasmodium ovale, Plasmodium vivax, and Plasmodium malariae. Gorillas and chimpanzees serve as reservoirs of infection. Humans may acquire malaria via the bites of the infected female Anopheles mosquitoes. Tropical and sub-tropical regions, such as Asia, sub-Saharan Africa, as well as Central and South America, are favorable for spreading malaria. 225 million cases of malaria are reported annually, and approximately 781,000 of those cases have fatal outcomes. Young children are most susceptible to this disease. Malaria can be prevented by utilizing insecticides and draining standing water where mosquitoes multiply.
Dengue virus causes dengue fever, which is an acute feverish infectious disease. The mosquito Aedes aegypti and sometimes Aedes albopictus can transmit dengue to people. Only humans serve as reservoirs of this virus. The dengue virus is prevalent in tropical and sub-tropical areas all over the world. More than 50 million people become infected by this disease yearly. Currently, dengue fever is endemic in approximately 110 countries. Control measures for the disease include personal protection (using repellents and avoidance of areas with mosquitoes) and the eradication of Aedes aegypti breeding locations within urban areas.
Leishmaniasis refers to a parasitic disease caused by protozoan parasites from Leishmania genus. People become infected via the bites of the sand flies that belong to the Phlebotominae subfamily. The most common reservoirs for leishmaniasis are hamsters and mice. This parasitic disease is found in southern Europe, tropics, and subtropics. Approximately a million cases of leishmaniasis occur annually, with 20,000 of them having fatal outcomes. Vector control, effective surveillance, and control of infected animals are the most appropriate control measures.
Arboviral encephalitides includes a number of acute infectious diseases caused by arboviruses (derived from “arthropod-borne virus”). These viruses enter the human body through the bites of bloodsucking arthropods, such as ticks, sand flies, mosquitoes, or midges. The diseases affect the central nervous system and lead to severe brain damage.
Vertebrate animals and birds represent the reservoirs for arboviral encephalitides. When female mosquitoes suckle the blood of an infected animal, they acquire the virus that replicates in their epithelial cells and infects their salivary glands. Therefore, they can transfer the virus to people during blood feeding.
Arboviruses that entail encephalitides in humans are sphere-shaped RNA viruses. They belong to the Flaviviruses and Alphaviruses genuses. Different arboviruses result in distinct forms of encephalitis. For instance, Flaviviruses are the main cause of St. Louis encephalitis, Murray Valley encephalitis, Japanese encephalitis, and tick-borne encephalitis. Alphaviruses lead to Eastern equine encephalitis and Western equine encephalitis. Different types of encephalitides tend to occur in various geographical areas. People more likely acquire these viruses during the period from June to September, whereas arthropods are most active during this time.
Elderly people, infants, and individuals with the weakened immune system are most susceptible to arboviruses. As a result, they frequently suffer from encephalitis. Currently, there is no effective treatment for arboviral encephalitides, and there are no vaccines that can prevent these diseases. Therefore, these diseases are the cause of a high rate of mortality among people worldwide. For instance, Japanese encephalitis prevails in Asian countries and leads to fatal outcomes. People who succeed to survive may develop permanent neuropsychiatric complications.
Emerging and re-emerging infectious diseases pose a considerable threat to the human health worldwide. Emerging disease refer to a previously unknown disease that tends to spread rapidly. A re-emerging disease, in its turn, represents the disease that progressed many years ago but returns again. There are factors that contribute to the development of these diseases.
Emerging infectious diseases appear due to evolutionary changes in existing microorganisms. Moreover, modern transportation allows diseases to spread to new geographic areas. Lastly, the areas that are undergoing significant ecologic changes enhance human exposure to unusual infections. H1N1 influenza, or the so-called swine flu, is an example of an emerging infectious disease. Influenza H1N1 represents a new virus that causes this type of influenza. It was detected in the United States in 2009 for the first time, and it spread rapidly throughout the world.
Re-emerging infectious diseases arise due to the ability of microorganisms to develop antibiotic resistance. Besides, microorganisms can be used as biological weapons in bioterrorism. In addition, environmental perturbation creates favorable conditions for the re-emergence of infectious diseases. For example, tuberculosis is one of re-emerging diseases. Individuals with HIV may easily acquire this life-threatening disease and transmit it to others. Drug-resistance complicates the treatment of tuberculosis, and it is often the cause of human death. Tuberculosis belongs to the diseases of poverty and is associated with inadequate hygiene and crowding. Whereas a number of people living in poverty is not reduced worldwide, it makes the above-mentioned disease difficult to control.
Emerging and re-emerging infectious diseases are the great challenge to humans. They increase the mortality rate all over the world. Lack of appropriate treatment and ecological changes contribute to a rapid progress of these disease. Bioterrorism also threatens human health and contributes to the spread of various severe infectious diseases.