1. The association between recent travel and risk of malaria: prospective cohort studies at 3 sites in Uganda with varied transmission intensity
ASTMH 66th annual meeting. Poster session C, Presentation number: 1634
Emmanuel Arinaitwe1,2, Bryan Greenhouse3, Isabel Rodriguez-Barraquer3, Joaniter I. Nankabirwa2, Simon Peter Kigozi1,2, John Rek2, Isaac Ssewanyana1,2, Arthur Mpimbaza2, Moses R. Kamya4, Philip J. Rosenthal3, Chris Drakeley1, Grant Dorsey3, Sarah G. Staedke1
1London School of Hygiene and Tropical Medicine, London, United Kingdom, 2Infectious Diseases Research Collaboration, Kampala, Uganda, 3Department of Medicine, University of California San Francisco, San Francisco, United States, 4School of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
Introduction
Malaria transmission is high in most areas of Uganda, however, transmission has declined in some areas due to urbanization and indoor residual spraying of insecticides (IRS)
People living in relatively low transmission areas may be at increased risk of malaria following recent overnight travel
The objective of this study was to evaluate associations between recent overnight travel and the incidence of malaria
Results
From July 2015 to June 2016, travel histories were taken from 906 participants in 3 study sites.
Most participants who travelled reported taking only one trip.
Reported use of LLINs during recent overnight travel was low (35.5%).
Among individuals who travelled, the incidence of malaria was 3 times higher in the 1-60 days after travelling as compared to periods without travel in the previous 60 days (1.15 vs episodes of malaria PPY, IRR=3.53, 95% CI , p<0.001)
On adjusting by age, this finding was statistically significant only in children (1.78 vs episodes of malaria PPY, IRR=3.67, 95% CI , p < 0.001).
Recent overnight travel was associated with a significantly higher risk of malaria incidence in all 3 study sites, most notably in Nagongera, where there was a 6-fold increase in the incidence of malaria during the post-travel period (0.14 vs episodes PPY, IRR=6.54, 95% CI , p=0.008).
Methods
Cohort studies were conducted at 3 sub-counties
Walukuba, a peri-urban area, with low malaria transmission
Nagongera, a rural area receiving IRS
Kihihi, a rural area with moderate transmission
All households within each sub-county were enumerated and 100 households randomly selected from each sub-county
All children years of age and one adult per household were enrolled
Routine evaluations were done every 3 months
Study participants received all care from study clinics open 7 days/week
Data on dates of recent overnight travel were collected at every visit
Overnight travel was defined as spending at least a night outside the sub-county of residence
Malaria, defined as fever in the presence of parasites detected by microscopy
The primary outcome: Incidence of malaria
Table. Characteristics of study sites, participants and travel history
Characteristic
Study site
All sites
Walukuba
Nagongera
Kihihi
Entomological inoculation rate1
N/A
2.4
4.5
11.2
Total number assessed for overnight travel
906
275
317
314
Number of children, n (% total)
687 (75.8%)
205 (74.6%)
242 (76.3%)
240 (76.4%)
Number of adult, n (% total)
219 (24.2%)
70 (25.5%)
75 (23.7%)
74 (23.6%)
Participants reporting any overnight travel, n (% total)
120 (13.3%)
64 (23.3%)
37 (11.7%)
19 (6.1%)
Characteristics of participants who reporting any recent overnight travel
Children, n (%)
69 (57.5%)
38 (59.4%)
25 (67.6%)
6 (31.6%)
Female gender, n (%)
75 (62.5%)
37 (57.8%)
20 (54.1%)
18 (94.7%)
Total duration of observation in days, median (IQR)
266 ( )
239 ( )
280 ( )
268 ( )
Total duration of overnight travel in days, median (IQR)
8 (4-19)
10 (6-21)
7 (3-13)
4 (2-16)
Number of overnight trips reported, n (%) 1 2 3
104 (86.7%)
14 (11.7%)
2 (1.7%)
55 (85.9%)
8 (12.5%)
1 (1.6%)
31 (83.8%)
5 (13.5%)
1 (2.7%)
1 (5.3%)
Characteristics of individual recent overnight trips
Total number of overnight trips
138 74 44 20
Duration of each trip, median (range)
7 (1-79)
8 (1-39)
7 (1-33)
5 (1-79)
Any reported LLIN use during travel, n (%)
49 (35.5%)
19 (25.7%)
23 (52.3%)
7 (35.0%)
Figure 1. Study area
1Infective bites per person year July 2015 – June 2016
Conclusions
Recent overnight travel was associated with a markedly higher incidence of malaria compared to the period before travel. These findings suggest that there is a need for targeted intervention to reduce the risk of malaria during overnight travel. The study was limited by small samples size to explore behavioural risk factors like staying outdoors late that might influence exposure to malaria.
Figure 2. Associations between recent overnight travel and incidence of malaria
Acknowledgements: Makerere University-UCSF Research Collaboration and Infectious Diseases Research Collaboration (IDRC) for administrative and technical support, the National Institutes of Health for financial support as part of the International Centers of Excellence in Malaria Research (ICMER) program (U19AI089674), and the Fogarty International Center for training support (D43TW7375).