Seasonal Prevalence of Mosquitoes, Including Vectors of Brugian Filariasis, in Southern Islands of the Republic of Korea

A survey of mosquitoes, including the vector status of Brugia malayi filariasis and their relative larval density, was conducted from 2002 to 2005 at several southern remote islands of Jeollanam-do (province), Gyeongsangnam-do, and Jeju-do, Korea, where filariasis was previously endemic. Overall, a total of 9 species belonging to 7 genera were collected. Ochlerotatus togoi (formerly known as Aedes togoi), Anopheles (Hyrcanus) group, and Culex pipiens were the predominant species captured at all areas. Oc. togoi larvae were most frequently collected at salinity levels <0.5% during June and July, with densities decreasing sharply during the rainy season in August. The most likely explanation for the eradication of filariasis in these areas is suggested to be an aggressive treatment program executed during the 1970s and the 1990s. However, high prevalence of the vector mosquitoes may constitute a potential risk for reemerging of brugian filariasis in these areas.

Two Cases of Brugian Filariasis Diagnosed Incidentally on Peripheral Blood Smears / 대한진단검사의학회지

The Brugian filariasis in Korea was once endemic in several areas including Jeju-do and small remote islands located in the southwestern part of the Korean peninsula. But recently it has almost been controlled. The first patient was a 42-year-old man, who visited the hospital with the chief complaints of fatigue, jaundice and edema on the right low extremity. Examination of a peripheral blood smear revealed non-megaloblastic macrocytic anemia, thrombocytopenia and eosinophilia, and a parasite, which was identified as microfilaria of Brugia malayi on the glass slide of blood obtained from the patient at midnight. The second patient was a 23-year-old man, who visited the hospital with the chief complaints of cough, sputum and fever. A parasite resembling that of the first patient was found in a peripheral blood smear accompaning neutrophilia. No more parasites, however, were found in the peripheral blood obtained from the patient at midnight. These two clinical cases of Brugian filariasis indicate that the clinical laboratory in Korea should be able to detect microfilariae for the diagnosis of filariasis.

Current status of Brugian filariasis in the Republic of the Philippines

Brugian filariasis in the Republic of the Philippines was first reported in 1964 or 63 years after Bancroftian filariasis was reported in this country. The etiologic agent is Brugian malayi with a nocturnal subperiodic type of microfilarial periodicity. The four endemic foci are Palawan, Sulu, Agusan and Eastern Samar, with prevalence rate of 30-64%;24%, 1.2% and 0.030% respectively. The mosquito vectors are Mansonia bonneae and Mansonia uniformis with infection rate and infective rate of 0.98% and 0.51% respectively from Quezon, Palawan. The biting activity of these mosquitoes is from about 1600 to 2200 which correspond to the rise in microfilarial density in the peripheral blood and takes approximately 10 days for the development of larvae to the infective stage within vector mosquito Diagnosis may be by the thick blood film method stained with Giemsa and/or Delafield hematoxylin, serologic method such as SAFA and intradermal test using B malayi antigen and by the use of nuclepore filter. Treatment of cases may b done with the use of Diethylcarbamazine (Hetrazan) 6 mg/kg. body weight daily for 12 days or a total dose of 72 mg/kg Brugian filariasis appears to be confined in areas where fresh water swamps are found which are ideal breeding sites for the mosquito vectors. Control may be achieved by reduction in the number of mosquito vectors; avoidance of bites of vector mosquitoes and elimination of microfilaremia by drug treatment. (Summary)