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The mosquito menace in the Philippines

Mosquito

What diseases can be transmitted by mosquitoes? Can you briefly describe them?

—ella_esterio@gmail.com

 

Mosquitoes can transmit many infectious diseases that are caused by a variety of microorganisms to people, but these diseases are mostly confined to certain geographical areas. In the Philippines, the mosquito-borne diseases include dengue, Chikungunya, Japanese encephalitis, malaria, and filariasis. Dengue, chikungunya, and Japanese encephalitis are caused by viruses while malaria and filariasis are caused by parasites.

 

Dengue and Chikungunya

Dengue and chikungunya have things in common. They are both caused by RNA viruses, albeit from different families. Also, they are transmitted by the same mosquitoes, Aedes aegypti and Aedes albopictus. Furthermore, their signs and symptoms, which appear three to seven days after a bite from an infected mosquito, are similar—high grade fever, joint pain, joint swelling, rash, headache, muscle pain, nausea, vomiting, and fatigue.  The two diseases differ, however, in that Chikungunya is generally more benign than dengue (serious complications and fatalities occur rarely), although the joint pains that it produces are often more severe and incapacitating.

 

Japanese Encephalitis

Japanese encephalitis (JE) is caused by the Japanese encephalitis virus (JEV) whose most important vectors are the mosquitoes Culex tritaeniorhynchus and Culex vishnui.

The vast majority of JEV infections are asymptomatic. Symptoms, if they occur, appear five to 15 days after the bite of an infected mosquito. They are flu-like and include headaches, fever, and fatigue and in children, nausea, vomiting, and abdominal pain. Although generally benign, one in 250 patients infected by JEV develop encephalitis (inflammation of the brain), which can be fatal, especially in children. Lifelong neurological defects such as deafness, emotionalliability, and hemi paresis may occur in those who survive the encephalitis.

 

Malaria

Malaria is a serious disease that is still a major public health problem in the Philippines, although the number of reported cases has been decreasing since 1990 because of the anti-malarial program of the government.

Malaria is caused by a parasite, a protozoon (i.e., a single-celled organism) that belongs to the genus plasmodium. There are four known species of this genus that cause disease in man—Plasmodium falciparum, P.vivax, P.ovale, and P. malariae—all are present in the Philippines.The parasites are transmitted to people through the bites of infected female Anopheles mosquitoes.

Malaria is present or endemic in all provinces of our country, except Cebu, Leyte, and Catanduanes, but most cases occur in rural areas, especially in forested, swampy, hilly, and mountainous regions—the preferred habitat of the mosquito vector.

The typical presentation of malaria is high grade fever that periodically recurs every after two to three days. The fever is preceded by several hours of chills and, as the fever subsides, the patient experiences marked sweating.

Malaria patients sooner or later develop anemia, but the more dreadful and sometimes fatal complications of the disease are kidney and liver failure, and cerebral malaria.

 

Filariasis

The causative agent of filarias is in the Philippines are two microscopic, thread-like roundworms: Wuchereriabancrofti (the more prevalent one) and Brugiamalayi. The former is transmitted by several species of Aedes, Culex, and Anopheles mosquitoes while the latter by at least two species of the Mansonia mosquito.

Repeated mosquito bites over several months to years are needed to get filariasis. Most people with filaria worms stay asymptomatic, but a small percentage will develop a condition called elepanthiasis, in which the limbs, genital organs, and the breasts swell to monstrous proportions.

According to our Department of Health (DOH), filariasis is endemic in 44 provinces in the Philippines but most cases occur in the rural areas of Bicol, Quezon, Mindoro, Masbate, Mindanao, Palawan, Agusan, and the Mountain Province. Also, seven provinces have reached elimination level already, namely: Southern Leyte, Sorsogon, Biliran, Bukidnon, Romblon, Agusandel Sur, and Dinagat Island.

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