Evaluation of the sentinel yellow fever surveillance system in Uganda, 2017-2022: strengths and weaknesses.

BACKGROUND: Uganda has a sentinel surveillance system in seven high-risk sites to monitor yellow fever (YF) patterns and detect outbreaks. We evaluated the performance of this system from 2017 to 2022. METHODS: We evaluated selected attributes, including timeliness (lags between different critical time points), external completeness (proportion of expected sentinel sites reporting ≥ 1 suspect case in the system annually), and internal completeness (proportion of reports with the minimum required data elements filled), using secondary data in the YF surveillance database from January 2017-July 2022. We conducted key informant interviews with stakeholders at health facility and national level to assess usefulness, flexibility, simplicity, and acceptability of the surveillance system. RESULTS: In total, 3,073 suspected and 15 confirmed YF cases were reported. The median time lag from sample collection to laboratory shipment was 37 days (IQR:21-54). External completeness was 76%; internal completeness was 65%. Stakeholders felt that the surveillance system was simple and acceptable, but were uncertain about flexibility. Most (71%) YF cases in previous outbreaks were detected through the sentinel surveillance system; data were used to inform interventions such as intensified YF vaccination. CONCLUSION: The YF sentinel surveillance system was useful in detecting outbreaks and informing public health action. Delays in case confirmation and incomplete data compromised its overall effectiveness and efficiency.

Sudan virus disease super-spreading, Uganda, 2022.

BACKGROUND: On 20 September 2022, Uganda declared its fifth Sudan virus disease (SVD) outbreak, culminating in 142 confirmed and 22 probable cases. The reproductive rate (R) of this outbreak was 1.25. We described persons who were exposed to the virus, became infected, and they led to the infection of an unusually high number of cases during the outbreak. METHODS: In this descriptive cross-sectional study, we defined a super-spreader person (SSP) as any person with real-time polymerase chain reaction (RT-PCR) confirmed SVD linked to the infection of ≥ 13 other persons (10-fold the outbreak R). We reviewed illness narratives for SSPs collected through interviews. Whole-genome sequencing was used to support epidemiologic linkages between cases. RESULTS: Two SSPs (Patient A, a 33-year-old male, and Patient B, a 26-year-old male) were identified, and linked to the infection of one probable and 50 confirmed secondary cases. Both SSPs lived in the same parish and were likely infected by a single ill healthcare worker in early October while receiving healthcare. Both sought treatment at multiple health facilities, but neither was ever isolated at an Ebola Treatment Unit (ETU). In total, 18 secondary cases (17 confirmed, one probable), including three deaths (17%), were linked to Patient A; 33 secondary cases (all confirmed), including 14 (42%) deaths, were linked to Patient B. Secondary cases linked to Patient A included family members, neighbours, and contacts at health facilities, including healthcare workers. Those linked to Patient B included healthcare workers, friends, and family members who interacted with him throughout his illness, prayed over him while he was nearing death, or exhumed his body. Intensive community engagement and awareness-building were initiated based on narratives collected about patients A and B; 49 (96%) of the secondary cases were isolated in an ETU, a median of three days after onset. Only nine tertiary cases were linked to the 51 secondary cases. Sequencing suggested plausible direct transmission from the SSPs to 37 of 39 secondary cases with sequence data. CONCLUSION: Extended time in the community while ill, social interactions, cross-district travel for treatment, and religious practices contributed to SVD super-spreading. Intensive community engagement and awareness may have reduced the number of tertiary infections. Intensive follow-up of contacts of case-patients may help reduce the impact of super-spreading events.

No Common Candidate Genes for Resistance to Fusarium graminearum, F. proliferatum, F. sporotrichioides, and F. subglutanins in Soybean (Glycine max L.) Accessions from Maturity Groups 0 and I: Findings from Genome-Wide Association Mapping.

Seedling diseases and root rot, caused by species of Fusarium, can limit soybean (Glycine max L.) production in the United States. Currently, there are few commercially available cultivars resistant to Fusarium. This study was conducted to assess the resistance of soybean maturity group (MG) accessions from 0 and I to Fusarium proliferatum, F. sporotrichioides, and F. subglutinans, as well as to identify common quantitative trait loci (QTL) for resistance to these pathogens, in addition to F. graminearum, using a genome-wide association study (GWAS). A total of 155, 91, and 48 accessions from the USDA soybean germplasm collection from maturity groups 0 and I were screened with a single isolate each of F. proliferatum, F. sporotrichioides, and F. subglutinans, respectively, using the inoculum layer inoculation method in the greenhouse. The disease severity was assessed 21 days post-inoculation and analyzed using non-parametric statistics to determine the relative treatment effects (RTE). Eleven and seven accessions showed significantly lower RTEs when inoculated with F. proliferatum and F. subglutinans, respectively, compared to the susceptible cultivar 'Williams 82'. One accession was significantly less susceptible to both F. proliferatum and F. subglutinans. The GWAS conducted with 41,985 single-nucleotide markers identified one QTL associated with resistance to both F. proliferatum and F. sporotrichioides, as well as another QTL for resistance to both F. subglutinans and F. graminearum. However, no common QTLs were identified for the four pathogens. The USDA accessions and QTLs identified in this study can be utilized to selectively breed resistance to multiple species of Fusarium.

Factors associated with acute watery diarrhea among children aged 0-59 months in Obongi District, Uganda, April 2022: A case-control study.

Background: Diarrheal diseases, are major concerns for Ugandan children; persistent in Obongi District despite high rotavirus vaccination rates (2019-2021). The district recorded the country's highest annual acute watery diarrhea (AWD) incidence from 2017 to 2021. Our study, conducted in April 2022, assessed AWD risk factors among 0-59-month-old children in Obongi. Methods: We conducted a 1:2 (193:386) unmatched case-control study. A case was a child (0-59 months) with ≥ 3 loose/liquid stools/day, negative malaria/pneumonia tests, residing in Itula/Parolinya subcounty from 1 to 30 April 2022. Medical records from 10 facilities were reviewed. Simple random sampling identified cases, who were interviewed, and controls were randomly chosen from non-AWD neighboring households. Child health cards provided vaccination details. We used logistic regression to identify factors associated with AWD. Results: Among 193 cases and 386 controls, 104 (54 %) cases and 183 (47 %) controls were male, 58 (30 %) cases and 127 (33 %) controls were aged 12-23 months, 187 (97 %) cases and 369 (96 %) controls had received at least one dose of rotavirus vaccine, 58 (30 %) cases and 120 (34 %) controls treated drinking water. Comorbidity presence (undernutrition, diabetes, HIV) (AOR = 12; CI: 2.5-53), caregiver's unwashed hands post-toilet (AOR = 3.9; CI: 1.2-13), and borehole vs. piped water (AOR = 4.0; CI: 1.7-9.6) linked to AWD. Conclusion: Modifiable factors, including failure of caregivers to wash their hands with soap after visiting toilets and use of borehole water were associated with AWD, suggesting that community sensitization on handwashing at critical times, using clean water and soap, and expanded use of piped water could reduce AWD incidence in this area.

Investigation of a bacterial meningitis cluster in a refugee settlement, Obongi District, Uganda, March 2023.

On 6 March 2023, Neisseria meningitidis serogroup C was isolated from a cerebral spinal fluid sample from Obongi District, Uganda. This sample was one of many from patients who were presenting with fever, convulsions, and altered consciousness. We investigated to determine the scope of the meningitis cluster, identify risk factors of contracting meningitis, and inform control measures. We reviewed medical records, conducted active community case finding, and conducted key informant interviews in the affected communities to identify cases and factors associated with contracting meningitis. We analysed case data by person, place, and time. Between 22 December 2022 and 1 May 2023, 25 cases with 2 deaths of bacterial meningitis occurred in Palorinya Refugee Settlement, Obongi District. Of these, 4 were laboratory-confirmed with Neisseria meningitidis serogroup C, 6 were probable cases, and 15 were suspected cases. Most (76%) of case-patients were <18 years old with a median age of 12 years (range 1-66 years). None of the case-patients was vaccinated against Neisseria meningitidis serogroup C. Each case-patient was from a different household and there was no epidemiological link between any of the cases. This meningococcal meningitis cluster caused by Neisseria meningitidis serogroup C occurred among non-vaccinated persons mostly aged <18 years in Palorinya Refugee Settlement. We recommended vaccination of at-risk persons.

Timeliness and completeness of monthly disease surveillance data reporting, Uganda, 2020-2021.

Introduction: timely and complete reporting of routine public health information about diseases and public health events are important aspects of a robust surveillance system. Although data on the completeness and timeliness of monthly surveillance data are collected in the District Health Information System-2 (DHIS2), they have not been routinely analyzed. We assessed completeness and timeliness of monthly outpatient department (OPD) data, January 2020-December 2021. Methods: we analyzed secondary data from all the 15 regions and 146 districts of Uganda. Completeness was defined as the number of submitted reports divided by the number of expected reports. Timeliness was defined as the number of reports submitted by the deadline (15th day of the following month) divided by reports received. Completeness or timeliness score of <80% was regarded incomplete or untimely. Results: overall, there was good general performance with the median completeness being high in 2020 (99.5%; IQR 97.8-100%) and 2021 (100%; IQR 98.7-100%), as was the median timeliness (2020; 82.8%, IQR 74.6-91.8%; 2021, 94.9%, IQR 86.5-99.1%). Kampala Region was the only region that consistently failed to reach ≥ 80% OPD timeliness (2020: 44%; 2021: 65%). Nakasongola was the only district that consistently performed poorly in the submission of timely reports in both years (2020: 54.4%, 2021: 58.3%). Conclusion: there was an overall good performance in the submission of complete and timely monthly OPD reports in most districts and regions in Uganda. There is a need to strengthen the good reporting practices exhibited and offer support to regions, districts, and health facilities with timeliness challenges.

Readiness of health facilities to manage individuals infected with COVID-19, Uganda, June 2021.

BACKGROUND: The COVID-19 pandemic overwhelmed the capacity of health facilities globally, emphasizing the need for readiness to respond to rapid increases in cases. The first wave of COVID-19 in Uganda peaked in late 2020 and demonstrated challenges with facility readiness to manage cases. The second wave began in May 2021. In June 2021, we assessed the readiness of health facilities in Uganda to manage the second wave of COVID-19. METHODS: Referral hospitals managed severe COVID-19 patients, while lower-level health facilities screened, isolated, and managed mild cases. We assessed 17 of 20 referral hospitals in Uganda and 71 of 3,107 lower-level health facilities, selected using multistage sampling. We interviewed health facility heads in person about case management, coordination and communication and reporting, and preparation for the surge of COVID-19 during first and the start of the second waves of COVID-19, inspected COVID-19 treatment units (CTUs) and other service delivery points. We used an observational checklist to evaluate capacity in infection prevention, medicines, personal protective equipment (PPE), and CTU surge capacity. We used the "ReadyScore" criteria to classify readiness levels as > 80% ('ready'), 40-80% ('work to do'), and < 40% ('not ready') and tailored the assessments to the health facility level. Scores for the lower-level health facilities were weighted to approximate representativeness for their health facility type in Uganda. RESULTS: The median (interquartile range (IQR)) readiness scores were: 39% (IQR: 30, 51%) for all health facilities, 63% (IQR: 56, 75%) for referral hospitals, and 32% (IQR: 24, 37%) for lower-level facilities. Of 17 referral facilities, two (12%) were 'ready' and 15 (88%) were in the "work to do" category. Fourteen (82%) had an inadequate supply of medicines, 12 (71%) lacked adequate supply of oxygen, and 11 (65%) lacked space to expand their CTU. Fifty-five (77%) lower-level health facilities were "not ready," and 16 (23%) were in the "work to do" category. Seventy (99%) lower-level health facilities lacked medicines, 65 (92%) lacked PPE, and 53 (73%) lacked an emergency plan for COVID-19. CONCLUSION: Few health facilities were ready to manage the second wave of COVID-19 in Uganda during June 2021. Significant gaps existed for essential medicines, PPE, oxygen, and space to expand CTUs. The Uganda Ministry of Health utilized our findings to set up additional COVID-19 wards in hospitals and deliver medicines and PPE to referral hospitals. Adequate readiness for future waves of COVID-19 requires additional support and action in Uganda.

Ownership and use of long-lasting insecticidal nets three months after a mass distribution campaign in Uganda, 2021.

BACKGROUND: Uganda conducted its third mass long-lasting insecticidal net (LLIN) distribution campaign in 2021. The target of the campaign was to ensure that 100% of households own at least one LLIN per two persons and to achieve 85% use of distributed LLINs. LLIN ownership, use and associated factors were assessed 3 months after the campaign. METHODS: A cross-sectional household survey was conducted in 14 districts from 13 to 30 April, 2021. Households were selected using multistage sampling. Each was asked about LLIN ownership, use, duration since received to the time of interview, and the presence of LLINs was visually verified. Outcomes were having at least one LLIN per two household members, and individual LLIN use. Modified Poisson regression was used to assess associations between exposures and outcomes. RESULTS: In total, 5529 households with 27,585 residents and 15,426 LLINs were included in the analysis. Overall, 95% of households owned ≥ 1 LLIN, 92% of the households owned ≥ 1 LLIN < 3 months old, 64% of households owned ≥ 1 LLIN per two persons in the household. Eighty-seven per cent could sleep under an LLIN if every LLIN in the household were used by two people, but only 69% slept under an LLIN the night before the survey. Factors associated with LLIN ownership included believing that LLINs are protective against malaria (aPR = 1.13; 95% CI 1.04-1.24). Reported use of mosquito repellents was negatively associated with ownership of LLINs (aPR = 0.96; 95% CI 0.95-0.98). The prevalence of LLIN use was 9% higher among persons who had LLINs 3-12 months old (aPR = 1.09; 95% CI 1.06-1.11) and 10% higher among those who had LLINs 13-24 months old (aPR = 1.10; 95% CI 1.06-1.14) than those who had LLINs < 3 months old. Of 3,859 LLINs identified in the households but not used for sleeping the previous night, 3250 (84%) were < 3 months old. Among these 3250, 41% were not used because owners were using old LLINs; 16% were not used because of lack of space for hanging them; 11% were not used because of fear of chemicals in the net; 5% were not used because of dislike of the smell of the nets; and, 27% were not used for other reasons. CONCLUSION: The substantial difference between the population that had access to LLINs and the population that slept under LLINs indicates that the National Malaria Control Programme (NMCP) may need to focus on addressing the main drivers or barriers to LLIN use. NMCP and/or other stakeholders could consider designing and conducting targeted behaviour change communication during subsequent mass distribution of LLINs after the mass distribution campaign to counter misconceptions about new LLINs.

Evaluation of public health surveillance systems in refugee settlements in Uganda, 2016-2019: lessons learned.

BACKGROUND: Civil wars in the Great Lakes region resulted in massive displacement of people to neighboring countries including Uganda. With associated disease epidemics related to this conflict, a disease surveillance system was established aiming for timely detection of diseases and rapid response to outbreaks. We describe the evaluation of and lessons learned from the public health surveillance system set up in refugee settlements in Uganda. METHODS: We conducted a cross-sectional survey using the US Centers for Disease Control and Prevention Updated Guidelines for Evaluating Public Health Surveillance Systems and the Uganda National Technical Guidelines for Integrated Disease Surveillance and Response in four refugee settlements in Uganda-Bidibidi, Adjumani, Kiryandongo and Rhino Camp. Using semi-structured questionnaires, key informant and focus group discussion guides, we interviewed 53 health facility leaders, 12 key personnel and 224 village health team members from 53 health facilities and 112 villages and assessed key surveillance functions and attributes. RESULTS: All health facilities assessed had key surveillance staff; 60% were trained on Integrated Disease Surveillance and Response and most village health teams were trained on disease surveillance. Case detection was at 55%; facilities lacked standard case definitions and were using parallel Implementing Partner driven reporting systems. Recording was at 79% and reporting was at 81%. Data analysis and interpretation was at 49%. Confirmation of outbreaks and events was at 76%. Preparedness was at 72%. Response was at 34%. Feedback was at 82%. Evaluate and improve the system was at 67%. There was low capacity for detection, response and data analysis and interpretation of cases (< 60%). CONCLUSION: The surveillance system in the refugee settlements was functional with many performing attributes but with many remaining gaps. There was low capacity for detection, response and data analysis and interpretation in all the refugee settlements. There is need for improvement to align surveillance systems in refugee settlements with the mainstream surveillance system in the country. Implementing Partners should be urged to offer support for surveillance and training of surveillance staff on Integrated Disease Surveillance and Response to maintain effective surveillance functions. Functionalization of district teams ensures achievement of surveillance functions and attributes. Regular supervision of and support to health facility surveillance personnel is essential. Harmonization of reporting improves surveillance functions and attributes and appropriation of funds by government to districts to support refugee settlements is complementary to maintain effective surveillance of priority diseases in the northern and central part of Uganda.

Examining the Interaction between Phytophthora sojae and Soybean Cyst Nematode on Soybean (Glycine max).

Phytophthora sojae and soybean cyst nematode (SCN) are important pathogens of soybean. Although these pathogens infect soybean roots, there is limited evidence of any interaction between them. The objective of this study was to examine the interaction between SCN and P. sojae on soybean in the greenhouse. Seeds of four soybean cultivars (Jack, Surge, Williams 82, Williams) were pre-germinated and placed in cone-tainers (Stuewe and Sons Inc., Tangent, OR, USA), containing a steam pasteurized sand-clay mixture. The experiment was set up in a completely randomized design with five replications and performed twice. Two P. sojae isolates were used in this study that represented two different virulence pathotypes (simple and complex pathotypes). For each isolate, soybean plants were not inoculated, inoculated with one of the treatments-SCN, P. sojae, and combination of P. sojae and SCN. After 35 DOI, stem length, root length, plant weight, root weight, lesion length, and SCN population were recorded. On all soybean cultivars with different types of incomplete resistance, the complex pathotype (PS-15-TF3) influenced the lesion length (mm) in the presence of SCN. However, the SCN population was reduced by both complex and simple pathotypes of P. sojae. This suggests that use both SCN and P. sojae resistance cultivars, can manage the disease complex and reduce soybean yield loss.

Investigation of a Cluster of Severe Respiratory Disease Referred from Uganda to Kenya, February 2017.

On February 22, 2017, Hospital X-Kampala and US CDC-Kenya reported to the Uganda Ministry of Health a respiratory illness in a 46-year-old expatriate of Company A. The patient, Mr. A, was evacuated from Uganda to Kenya and died. He had recently been exposed to dromedary camels (MERS-CoV) and wild birds with influenza A (H5N6). We investigated the cause of illness, transmission, and recommended control. We defined a suspected case of severe acute respiratory illness (SARI) as acute onset of fever (≥38°C) with sore throat or cough and at least one of the following: headache, lethargy, or difficulty in breathing. In addition, we looked at cases with onset between February 1 and March 31 in a person with a history of contact with Mr. A, his family, or other Company A employees. A confirmed case was defined as a suspected case with laboratory confirmation of the same pathogen detected in Mr. A. Influenza-like illness was defined as onset of fever (≥38°C) and cough or sore throat in a Uganda contact, and as fever (≥38°C) and cough lasting less than 10 days in a Kenya contact. We collected Mr. A's exposure and clinical history, searched for cases, and traced contacts. Specimens from the index case were tested for complete blood count, liver function tests, plasma chemistry, Influenza A(H1N1)pdm09, and MERS-CoV. Robust field epidemiology, laboratory capacity, and cross-border communication enabled investigation.

Comprehensive knowledge of HIV prevention among fishing communities of Lake Kyoga, Uganda, 2013.

BACKGROUND: Compared to the general population in Uganda, fishing communities suffer greater burden of HIV/AIDS. We determined the level of comprehensive knowledge on HIV prevention and its associated factors among fishing communities of Lake Kyoga. METHODS: We conducted secondary analysis of data from the Lake Kyoga Behavioral Survey, a population-based sample survey on behavioral risk factors for HIV, syphilis, and schistosomiasis among adults in fishing communities of Lake Kyoga in 2013. We defined comprehensive knowledge as having correct knowledge on HIV prevention (consistent condom use, faithfulness, a healthy-looking person can have HIV, and HIV cannot be transmitted through food-sharing, witchcraft or handshake). We used logistic regression to determined potential factors associated with comprehensive knowledge on HIV prevention and control for confounding. RESULTS: Of 1780 persons in the sample, 51% (911/1780) were females. The mean age was 32 (range: 15-97) years. Overall, 51% (899/1780) of persons had comprehensive knowledge on HIV prevention. Level of comprehensive knowledge on HIV prevention was similar between females (52%, 449/911) and males (49%, 450/869). Males (76%, 658/869) had lower knowledge on HIV transmission from mother to child during breast feeding compared to females (81%, 738/911) (p-value 0.019). Fishermen (46%,324/711) who lived > 5 km away from a health center compared to 54% (572/1066) who lived within 5 km radius were less likely to have comprehensive knowledge on HIV prevention (PRRadj = 0.8; 95%CI = 0.5-0.92). Those who had ever tested for HIV were more likely to have comprehensive knowledge of HIV transmission (PRRadj = 1.1; 95% 1.03-1.70). CONCLUSION: Half of the population of Lake Kyoga fishing community had comprehensive knowledge of HIV prevention. Long distances from health facilities reduced the level of comprehensive knowledge on HIV transmission. HIV testing increased the level of comprehensive knowledge on HIV transmission. Ministry of health should ensure that HIV/AIDS information; education and communication and HIV counseling and testing activities are intensified in fishing communities of Lake Kyoga, with more emphasis on communities living in distances of more than 5 km away from the health facility.

A cholera outbreak caused by drinking contaminated river water, Bulambuli District, Eastern Uganda, March 2016.

BACKGROUND: A cholera outbreak started on 29 February in Bwikhonge Sub-county, Bulambuli District in Eastern Uganda. Local public health authorities implemented initial control measures. However, in late March, cases sharply increased in Bwikhonge Sub-county. We investigated the outbreak to determine its scope and mode of transmission, and to inform control measures. METHODS: We defined a suspected case as sudden onset of watery diarrhea from 1 March 2016 onwards in a resident of Bulambuli District. A confirmed case was a suspected case with positive stool culture for V. cholerae. We conducted descriptive epidemiologic analysis of the cases to inform the hypothesis on mode of transmission. To test the hypothesis, we conducted a case-control study involving 100 suspected case-patients and 100 asymptomatic controls, individually-matched by residence village and age. We collected seven water samples for laboratory testing. RESULTS: We identified 108 suspected cases (attack rate: 1.3%, 108/8404), including 7 confirmed cases. The case-control study revealed that 78% (78/100) of case-patients compared with 51% (51/100) of control-persons usually collected drinking water from the nearby Cheptui River (ORMH = 7.8, 95% CI = 2.7-22); conversely, 35% (35/100) of case-patients compared with 54% (54/100) of control-persons usually collected drinking water from borehole pumps (ORMH = 0.31, 95% CI = 0.13-0.65). The index case in Bwikhonge Sub-county had onset on 29 February but the outbreak had been on-going in the neighbouring sub-counties in the previous 3 months. V. cholera was isolated in 2 of the 7 river water samples collected from different locations. CONCLUSIONS: We concluded that this cholera outbreak was caused by drinking contaminated water from Cheptui River. We recommended boiling and/or treating drinking water, improved sanitation, distribution of chlorine tablets to the affected villages, and as a long-term solution, construction of more borehole pumps. After implementing preventive measures, the number of cases declined and completely stopped after 6th April.

Spatio-temporal patterns in kdr frequency in permethrin and DDT resistant Anopheles gambiae s.s. from Uganda.

The planned upscaling of vector control strategies requires insight into the epidemiological consequences of vector resistance. Therefore, the pyrethroid and DDT resistance status of Anopheles gambiae s.l. was assessed in Uganda from 2004 to 2006, and spatial and seasonal variations in knockdown resistance (kdr) frequencies were analyzed in terms of epidemiological significance. Anopheles gambiae s.l. was DDT and pyrethroid resistant in central and eastern Uganda. The L1014S kdr allele frequencies varied from 3% to 48% in An. gambiae s.s. Although the homozygous resistant genotype was the most prevalent genotype among survivors, the genotypes could not entirely explain the bioassay results. In the dry season, the kdr frequency was significantly higher in Plasmodium falciparum-infected mosquitoes, indicating that mosquitoes bearing a kdr mutation have a better adult survival, hence a higher likelihood of becoming infectious. This study showed that kdr might have an epidemiological impact that could jeopardize the vector control strategies.

Intensity of malaria transmission and the spread of Plasmodium falciparum resistant malaria: a review of epidemiologic field evidence.

Malaria transmission intensity has been proposed, based on theoretical models, as an important factor for the spread of falciparum-resistant malaria, but the predictions obtained vary according to the assumptions inherent in the model used. We summarized the available field data on transmission intensity and the prevalence of malaria drug resistance. Resistance to chloroquine and sulphadoxine-pyrimethamine monotherapy was invariably higher where transmission was intense. Vector control interventions were associated with a better chloroquine and sulfadoxine-pyrimethamine efficacy. However, high resistance to chloroquine and also to combination therapy (chloroquine plus sulphadoxine-pyrimethamine and amodiaquine plus sulfadoxine-pyrimethamine) was also observed in very low transmission areas. Reducing transmission intensity is likely to slow the spread of drug resistance. Nevertheless, where transmission is extremely low, to limit the unnecessary use of antimalarials and a consequent paradoxical acceleration of the spread of resistance, patients should be treated only after laboratory confirmation of malaria.

Variation in malaria transmission intensity in seven sites throughout Uganda.

Knowledge of the baseline malaria transmission in a given environment is important to guide malaria control interventions. However, in Uganda, recent information on malaria transmission intensity is lacking. Therefore, a 1-year entomological study was conducted in seven ecologically different sites throughout the country to assess spatial and temporal patterns in malaria transmission intensity. Anopheles gambiae sensu stricto was the main vector in five of the seven study sites, and An. funestus was the most important vector in the two other sites. In a peri-urban village, An. arabiensis contributed substantially to malaria transmission. Clear differences in annual entomological inoculation rates (AEIR) were observed between the study sites, ranging from 4 infective bites per person per year in the southwestern part of the country to >1,500 infective bites per person per year in a swampy area near the Nile River. Between villages with parasite prevalences of >or= 80% in children between 1 and 9 years old, a 4-fold difference in AEIR was observed. Based on the observed behavior of the vectors, insecticide-treated bed nets will be highly effective in controlling malaria. However, in the high transmission areas, additional measures will be needed to reduce the malaria burden to acceptable levels.