Study to Understand Resistance to Malaria in Vietnam

The Hospital for Tropical Diseases and the Oxford University Clinical Research Unit in Vietnam have recruited severe malaria cases, healthy controls and relatives of some of the cases to contribute to Consortial Project 1. Individuals were recruited over an 18 year period at the Hospital for Tropical Diseases, a tertiary referral hospital, in Ho Chi Minh City (majority referred from the remote border provinces and central highlands of the country) and 2 provincial hospitals in Bình Phước province. Bình Phước province is a low highland region in south central Vietnam. It has low seasonal transmission of Plasmodium falciparum and P. vivax mainly in the forested rural areas. Entomological inoculation rates are very low (in most areas <1). The majority of those recruited were of the Vietnamese Kinh ethnicity.

Description of study population - Cases

Cases consist of children and adults (8 mnths-79 yrs) admitted to hospital with signs of severe malaria, recruited during four studies. Three studies recruited in the Hospital for Tropical Diseases between 1991-1995, 1996-2001 and an ongoing study started in 2006. The fourth study recruited in both the Hospital for Tropical Diseases and two provincial hospitals in Bình Phước province between 2000-2006.

The entry criteria for severe malaria cases generally included the presence of asexual parasitemia and at least one of the following: impaired consciousness (Glasgow coma scale<12 or Blantyre coma score<5); severe anaemia (hematocrit<20% and parasitaemia>100,000/ml or hematocrit<15% or hemoglobin<<5g/dl); repeated convulsions; acidosis (HCO3<15mmol/l or lactate>4mmol/l); renal impairment; jaundice; hyperparasitaemia (>10% or >100,000 parasites/ml or >500,000/ml); respiratory distress; and hypoglycemia (blood glucose <20mg/dl or <40mg/dl).

Description of study population - Controls

Cord blood control samples were collected from babies born in 2003 and between 2006-2007 at the Hung Vuong Obstetric Hospital in Ho Chi Minh City and from babies born in 2003 at Dong Thap Hospital in Dong Thap province. In addition community controls were recruited which were individually matched to a proportion of the severe malaria cases by age (0-73 yrs), gender, ethnicity and location. Potential community controls were questioned about any possible history of severe malaria or time spent in hospital. Any who had spent more than 48 hours in hospital other than for an operation, injury or known non-malaria diagnosis were excluded.

Description of study population - Relatives

Blood samples from the relatives of some of the severe malaria cases were collected. These were mainly parents.