Vector-Borne Diseases   

Vector-Borne Diseases

The word "disease" is not something new to us. However, how many of us know how different diseases can be transmitted in different ways? How many of us have heard of the term "vector-borne disease"? Vectors refer to organisms, mostly arthropods or insects, such as ticks, sandflies, blackflies or mosquitoes, which serve as the host of carrying and transferring a pathogen (a biological agent that may cause disease or illness to its host) from one host to another. Some hosts are not affected by this pathogen and are known as reservoirs. These pathogens remains within a particular vector’s populations of reservoir until transmitted to another host (including humans) via vectors.

Many different types of diseases are transmitted in this way. However, we will only mention a few here. One of the more important ones includes malaria. The pathogens responsible for human malaria are of four different species of the protozoan parasite Plasmodium. These include Plasmodium falciparum, P. vivax, P. ovale and P. malariae. The malaria parasites are transmitted by various species of Anopheles mosquitoes.

They feed on human blood mainly between sunset and sunrise. Dengue fever is another vector-borne disease. It is transmitted via mosquitoes; more specifically the Aedes aegypti mosquito, which bites during the daylight. In this case, there are no direct person-to-person transmissions, while monkeys sometimes act as a reservoir host in Southeast Asia and West Africa.

In recent years, vector-borne diseases have been on the rise. According to the World Health Organization (WHO), it has been estimated that a child dies of malaria every 30 seconds; with most of these deaths occurring in sub-Saharan Africa, South Asia, Central and South America, and the Western Pacific. In 2005, dengue is the most important mosquito-borne viral disease affecting humans, with its global distribution comparable to that of malaria. Each year, tens of millions of cases of dengue fever occur, and an estimated 2.5 billion people live in areas at risk for epidemic transmission.

The causes

What causes these diseases to be on the rise? Some global changes such as global warming are among the reasons for the increase of vector-borne diseases. Global warming has cause increase of heat and humidity. Such changes will create suitable growth conditions for vectors’ proliferation. Although vector-borne diseases are currently prevalent in the tropical and subtropical regions, climate change could create conditions suitable for outbreaks in temperate regions as well. Therefore, it is extremely important to know what causes these outbreaks and what can be done to curb them.

Vector-borne diseases often (but not exclusively) affect people and families who are suffering from poverty. Debilitating living conditions, such as unhygienic water sources, creates suitable places for vectors, such as mosquitoes, to breed. The houses that they live in are poorly constructed and often have poor or proper water storage facilities. This increases the risk of contracting vector-borne diseases such as malaria by at least 2.5 times more than those who live in houses of good construction. When combined with factors such as malnutrition, poor health conditions or gastrointestinal diseases, the risk of contracting diseases increases. These scenarios can be boiled down to the world’s population boom and uncontrolled urbanization that cause major demographic changes around the world. These changes have resulted in substandard housing and inadequate water, sewer, and waste management systems, all of which can increase the prevalence of vector-borne diseases globally. Thus, such diseases will concern everyone all over the world, not just the poor or those living in tropical regions.

It is always better to prevent than to cure. Much of the public is still not aware of the dangers of these vector-borne diseases. Those in highly affected areas are still not properly informed or educated. A simple or small start can always lead to improvement, especially when the methods are effective. Simple poster displays in local languages can be really helpful. These posters may include messages such as the early identification of disease symptoms, and the need to maintain attendance for drug delivery. In the case of dengue, tourists who are often at high risk of contracting this disease when they visit tropical regions are advised to reduce their risk by remaining in well-screened or air-conditioned areas when possible, wearing clothing that adequately covers the arms and legs. They should also apply insect repellant to both skin and clothes. In general, the prevention of mosquito bites by using insect repellant, bed nets, and clothing that covers most of the body is one of the best ways to curb such vector-borne diseases. The public should be made aware that it is their responsibility to help control the spread of these outbreaks as well, and not just the government’s.

With medical advancement, it is not impossible to control the spread of these diseases. Many modern drugs such as atovaquone and chloroquine (antimalarial drugs), have been developed and are highly effective in treating the diseases.


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