This is an observational study (case-control study) aiming to identify risk factors for malaria infection in health centers or malaria posts or district hospitals in Buntharik District and Nachalui District, Ubon Ratchathani Province, Thailand.

This study expects to recruit 330 cases (malaria positive) and 330 control (negative cases) subject. One-to-one matching of cases (malaria positive) and controls (malaria negative) will be done at each study site.

CASE (Malaria positive) subject will go through the following;

1. Enrollment visit (Day 0)

   1.1 Blood collection of three dried blood spots, and malaria slide. In district hospitals in individuals >14 kg: additional 10ml venous blood will be collected.

   1.2 A survey questionnaire which includes patient demographics, information on malaria treatment, bed net use and possible risk factors for acquiring malaria, as well as questions about their travel and usage of mobile phones will be administered.

2. Follow up visits (if fever plus Day 42 (+/-3))

2.1 Blood collection of three dried blood spots and malaria slide. In district hospitals: additional 0.5ml venous blood will be collected.

2.2 Short survey questionnaire including questions on symptoms, travel and possible risk behaviors since enrollment will be administered.

CONTROL (Malaria negative) subject will go through the following;

1. Enrollment visit (Day 0)

   1.1 Blood collection to confirm negative malaria slide. In district hospitals: additional 0.5ml venous blood will be collected.

   1.2 A survey questionnaire including patient demographics, information on any recent malaria treatment they may have taken, bed net use and possible risk factors for acquiring malaria, as well as questions about their travel and usage of mobile phones will be administered.

2. Follow up visit: No follow up visit

Study sites and enrollment:

Patients self-presenting to (1) health centres or(2) malaria posts or (3) district hospitals in Buntharik District and Nachalui District, Ubon Ratchathani Province, Thailand and requiring a diagnostic test for malaria as determined by the treating clinician will be recruited. Those who are malaria positive will be candidate cases and those who are malaria negative will be candidate controls.

One-to-one matching of cases and controls will be done at each study site. One control will be matched to each case. The matching criteria will be the next malaria negative patient to attend the study site of the same gender and age+/-5 years as an enrolled malaria positive case.

Study procedure:

CASE (Malaria patient defined by positive RDT or blood smear)

Upon enrollment, the below study procedures will be followed;

1. Blood samples consisting of:

   • Three dried blood spots
   • A microscopy slide
   • In the district hospitals only, 10 ml of venous blood will be taken from the positive for malaria patient.

2. A survey include patient demographics, information on malaria treatment, bed net use and possible risk factors for acquiring malaria, as well as questions about their travel and usage of mobile phone will be administered to each patient.

CONTROL (Non-malaria patient defined by negative RDT or blood smear)

Upon enrollment, for those negative for malaria, the below study procedures will be follows;

1. Blood samples consisting of:

   • Blood smear
   • In the district hospitals only, 0.5 ml of venous blood will also be collected.

2. A survey include patient demographics, information on malaria treatment, bed net use and possible risk factors for acquiring malaria, as well as questions about their travel and usage of mobile phone swill be administered to each patient.

CASE: Follow-up

• If patients develop a fever after the end of antimalarial treatment and within 42 days after enrollment, they will be asked to return for follow-up as soon as possible on one occasion and then again at 42 (+/-3) days.
• If they do not develop fever within 42 days after enrollment, they will be asked to return for follow up at 42 (+/-3) days.

At the follow-up visit, blood will be taken to test for malaria by microscopy, three dried blood spots will be taken and a short survey administered including questions on symptoms, travel and possible risk behaviors since enrollment.

*In the district hospitals only, 1.5ml of venous blood will be taken

CONTROL: No follow up

Inclusion Criteria:

- Case (Malaria patient defined by positive RDT or blood smear):

• Patients of ≥ 6 months of age testing positive for malaria of any species as determined by a positive rapid diagnostic test (RDT) or asexual stage parasites on a smear of peripheral blood including individuals with more than one species of Plasmodium.

  • Control (Non-malaria patient defined by negative RDT or blood smear):

• Patients > 6 months of age requiring a diagnostic test for malaria but testing negative for malaria by rapid diagnostic test (RDT) or asexual stage parasites on a smear of peripheral blood. Controls will be age and gender matched to individual cases at each study site (details below).

Exclusion Criteria:

Not willing to provide written informed consent.

Patients self-presenting to health centres or malaria posts or district hospitals in Buntharik District and Nachalui District, Ubon Ratchathani Province, Thailand and requiring a diagnostic test for malaria as determined by the treating clinician will be recruited. Those who are malaria positive will be candidate cases and those who are malaria negative will be candidate controls.

According to Mahidol-Oxford Tropical Medicine Research Unit policy