\ \ \ I wai; associntcd \\itl1 history of drinking untreated,vate. r and exposure to crowded, unsanitary conditions. Diagnosis is based 011 lhc dctcclion ofthe organism from the stools. It has been observed from dirccl fr:cal smear but sensitivity of llic lahoratory prnceclurc is improved through U1e Formalin Ether Conrcntrntion Tcd1nique (FECT). The blastocysts v;i ry in si:r. c with a dlametrr rang. ing from about 6 to 40 pm. '111cy arn generally spherical provided with a centrol hody tlrnl occllpics about 90% of the cell. Because of U1e large centra J body, nuclei of the parasite are almost always pushed to Ille periphery cell. I:rom a i;tudy of foodl1and lers in a tertiary hospital located in Met To Manila and canleens operating in the University belt of the City of Manila, 40% and 24% of the students examined were found positive for Blastocystis cysts respective ly. VECTOR-BORNE PARASITES There are certain groups of living things that carry and transntit infective agents to man. Some mechanically transmit the pat J10gens like the mes and cockroaches, while in some vectors, like mosquitoes, these infective agents undergo development anc. J mtlltiplication. To. is St. >ction covers parasites that are transmitted l J1rough these vectors. Plasmodia There are four species of Pl. asmodia causing malaria in man, namely: Plasmodium falcipnn1m, Plasmodium vivax, Plasmodium malariae and Plasmodfom ovale. All of these $pecies are transmitted through the bite of the infected female mosquitoes belonging lo the Genus Anopheles. lo the Philippines, the major mosquito vector is the female Anopheles minimusjlavirostris. TI1e most common cat Lc;e of malaria in the Phi Jjppines is Plasmodium falciparum. About 70% of all malaria cases are due to P. falciparum, 30% are due to P. vivax and less than 1% is due to P. malariae. P/asmodium ouale,however, is believed to be absent in the Philippin~. On the other hand, a monkey malarial parasite aillad Pla1;modium k'llowlo>si was identified from indigenous people in Mindanao by the Research Institute for Tropic Medicine. Among Lhe Plasmodia species, P. falciparum is considered to be the most dangerous because it causes severe complications such as cerebral involve. meat. Among children in endemic areas, chronic infection with malaria can lead to childhood anemia. Pregnant women whe. n infected wilh malaria may suffer from stillbirths and abortion. Plasmodia undergo an ase>mal method of multiplication in man called sd1izogony and g,ametogony. This makes mao as the intennedial e hos1. The ase,mal multiplication is periodic am! lhe lens:th of schi2. ogony differs from one species to another 111e sexual method of multiplication called sporogony occurs in the mosquito, the definitive host. ln man tbe malarial parasites undergo sdli:1. ogony in the red blood cells and for this reason, these parasitesmey be1Tansmitted throu&hjndiscretc hlood transfusion. Stages that di-vdop during i;chi~ony are trophozoi K-s which "il J then become schizonts, inside (lf which are merowiles. Schi1. ogony was shorte..:;t in P. falcjparum but lon&est \ \ in P. malariac. 111e highest number of mer01. oitcs :ire produced by P. fa lciparnm. while the fowe;. 1 are producl'd by P. malariae_ When the sd,izonts arc mature, t J1c host red \ \ \ ~~■----378ce-llsru-ptur-ea. J-1dth-eme'rowites' ar-ereleased-intothccir-ciilntjon_. ltis-al thispoinl■w■·■h■c■n-ia!· ~-