Likoma Island Research Articles

Description of a rock-dwelling cichlid that re-invaded the sand substrate in Lake Malai, Africa.

Pseudotropheus Regan had been a catch-all genus for many of the rock-dwelling cichlids of Lake Malai, known as mbuna, for over half a century. Although many of the species previously assigned to this genus have since been allocated to other genera there are still about a dozen species in the genus that do not appear to be closely related to its type species, P. williamsi, but for which no better placement could be found. Pseudotropheus livingstonii (Boulenger) is one such species and the new species described herein appears to be closely related and has for that reason been temporarily assigned to Pseudotropheus. Pseudotropheus likomae n. sp. from Likoma Island can be diagnosed from all other Pseudotropheus spp., by having five or fewer distinct vertical bars below the dorsal fin and two horizontal stripes in mature individuals.

Institutional, technical and financial sustainability of rural piped drinking water supply on a freshwater island: Case study of Likoma Island, Malawi

AbstractSustainable Development Goal 6 addresses the protection for both drinking water and lakes, and this is especially important for residents of a freshwater island. This study explores the institutional, technical and economic sustainability of a piped drinking water system operating on Likoma Island in Lake Malawi. Data were collected through household surveys and an analysis of historical records. Proximity and accessibility analyses were also conducted for households (n = 185) and their water sources. The results indicated that within 10 years after implementation of the system, 98% of the respondents had piped drinking water within 250 m of their households. Challenges to system sustainability unique to an island setting include the need for boat transportation, inconsistent electrical power supply and lack of island banking services. Factors contributing to broader system success include fishing households with cash income, limited dependence on communal taps, a strong mainland partner, tourism‐supported financial management, high payment rate amongst government institutions, system costs covered by pricing of water for customers and a manager with a high level of decision‐making authority. Opportunities to make the system more sustainable include reducing non‐revenue water losses, using drones or buying a dedicated boat for transport to the island and improving self‐sufficiency on the island to respond to equipment emergencies. Rural drinking water supplies in remote lake island communities must meet unique requirements for sustainable operation, and the institutional, technical and economic sustainability factors of Likoma Island illustrate a successful system likely to sustainably continue its operations into the future.

Assessment of catch composition and economic analysis of monofilament and multifilament under-meshed gears (Ngongongo) at Likoma Island, Lake Malawi

The study was conducted to assess catch composition and economic analysis of monofilament and multifilament under-meshed gillnets (Ngongongo) from March to April 2018 at Likoma Island, Lake Malawi. Catch efficiency for targeted fish species in monofilament gillnets showed that catch per unit effort (CPUE) was three times higher than that of multifilament gillnets for Copadichromis spp. (402.2 Kg, 43.3%), Opsaridium microcephulus (315.47 Kg, 34.6%), Rhamphocromis spp. (26.2 Kg, 2.8%), Bagrus meridionalis (21.6 Kg, 2.3%), Oreochromis karongae (40.7 Kg, 4.4%), Bathyclarias spp. (23.2 Kg, 2.5%), Dimidiochromis kiwinge ( 14.4Kg, 1.6%) among others. Catches for Copadichromis spp. comprised of 43% for both gillnet material type combined indicating the importance of this species in gillnet fishery in the district. Monofilament gillnet caught the highest number of fish (7569) while multifilament gillnet caught the least (5427). Again monofilament gillnet has the highest weight of fish (692.87kg) while multifilament has the least (238.22kg). T-test analysis showed that the weight of fish caught by monofilament and multifilament gillnets were significantly different from one another (p=0.000).The profitability performance non-motorized monofilament and multifilament gillnets canoe fisheries in Lake Malawi (Likoma) recorded profit margins at the end of the first year of operation with the minimum Return on Investment (ROI) of 58.9% and 34.4% respectively. On the other hand, the motorised monofilament and multifilament Gillnets canoe fisheries recorded loss 51.1% and 74.4% ROI. The study results point out to recommend for management interventions be put in place to manage the Lake Malawi fishery by imposing restrictions on effort, gear type and mesh sizes and access to illegal material.

Age differences between sexual partners, behavioural and demographic correlates, and HIV infection on Likoma Island, Malawi.

Patterns of age differences between sexual partners – “age-mixing” – may partially explain the magnitude of HIV epidemics in Sub-Saharan Africa. However, evidence of age-disparity as a risk factor for HIV remains mixed. We used data from a socio-centric study of sexual behaviour in Malawi to quantify the age-mixing pattern and to find associations between relationship characteristics and age differences for 1,922 participants. Three age difference measures were explored as predictors of prevalent HIV infection. We found that for each year increase in male participant age, the average age difference with their partners increased by 0.26 years, while among women it remained approximately constant around 5 years. Women in the study had larger within-individual variation in partner ages compared to men. Spousal partnerships and never using a condom during sex were associated with larger age differences in relationships of both men and women. Men who were more than five years younger than their partners had 5.39 times higher odds (95% CI: 0.93–31.24) of being HIV-infected than men 0–4 years older. The relationship between HIV-infection and age-asymmetry may be more complex than previously described. The role that women play in HIV transmission should not be under-estimated, particularly in populations with large within-individual variation in partner ages.

Schistosomiasis in Malawi: a systematic review.

IntroductionSchistosomiasis remains an important public health problem that undermines social and economic development in tropical regions of the world, mainly Sub-Saharan Africa. We are not aware of any systematic review of the literature of the epidemiology and transmission of schistosomiasis in Malawi since 1985. Therefore, we reviewed the current state of knowledge of schistosomiasis epidemiology and transmission in this country and identified knowledge gaps and relevant areas for future research and research governance.MethodsWe conducted computer-aided literature searches of Medline, SCOPUS and Google Scholar using the keywords: “schistosomiasis”, “Bilharzia”, “Bulinus” and “Biomphalaria” in combination with “Malawi”. These searches were supplemented by iterative reviews of reference lists for relevant publications in peer reviewed international scientific journals or other media. The recovered documents were reviewed for their year of publication, location of field or laboratory work, authorship characteristics, ethics review, funding sources as well as their findings regarding parasite and intermediate host species, environmental aspects, geographical distribution, seasonality of transmission, and infection prevalence and intensities.ReviewA total of 89 documents satisfied the inclusion criteria and were reviewed. Of these, 76 were published in international scientific journals, 68 were peer reviewed and 54 were original research studies. Most of the documents addressed urinary schistosomiasis and about two thirds of them dealt with the definitive host. Few documents addressed the parasites and the intermediate hosts. While urinary schistosomiasis occurs in most parts of Malawi, intestinal schistosomiasis mainly occurs in the central and southern highlands, Likoma Island and Lower Shire. Studies in selected communities estimated prevalence rates of up to 94.9% for Schistosoma haematobium and up to 67.0% for Schistosoma mansoni with considerable geographical variation. The main intermediate host species are Bulinus globosus and Bulinus nyassanus for urinary schistosomiasis and Biomphalaria pfeifferi for intestinal schistosomiasis. Seasonality of transmission tends to vary according to geographical, environmental, biological and behavioural factors.ConclusionTransmission of schistosomiasis in Malawi appears to be highly focal, with considerable variation in space and time. Many locations have not been covered by epidemiological investigations and, thus, information on the transmission of schistosomiasis in Malawi remains fragmented. Functional infection risk assessment systems based on systematic investigations and surveillance are required for developing informed prevention and control strategies.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-014-0570-y) contains supplementary material, which is available to authorized users.

Sample size considerations in the design of cluster randomized trials of combination HIV prevention

Background Cluster randomized trials have been utilized to evaluate the effectiveness of HIV prevention strategies on reducing incidence. Design of such studies must take into account possible correlation of outcomes within randomized units. Purpose To discuss power and sample size considerations for cluster randomized trials of combination HIV prevention, using an HIV prevention study in Botswana as an illustration. Methods We introduce a new agent-based model to simulate the community-level impact of a combination prevention strategy and investigate how correlation structure within a community affects the coefficient of variation - an essential parameter in designing a cluster randomized trial. Results We construct collections of sexual networks and then propagate HIV on them to simulate the disease epidemic. Increasing level of sexual mixing between intervention and standard-of-care (SOC) communities reduces the difference in cumulative incidence in the two sets of communities. Fifteen clusters per arm and 500 incidence cohort members per community provide 95% power to detect the projected difference in cumulative HIV incidence between SOC and intervention communities (3.93% and 2.34%) at the end of the third study year, using a coefficient of variation 0.25. Although available formulas for calculating sample size for cluster randomized trials can be derived by assuming an exchangeable correlation structure within clusters, we show that deviations from this assumption do not generally affect the validity of such formulas. Limitations We construct sexual networks based on data from Likoma Island, Malawi, and base disease progression on longitudinal estimates from an incidence cohort in Botswana and in Durban as well as a household survey in Mochudi, Botswana. Network data from Botswana and larger sample sizes to estimate rates of disease progression would be useful in assessing the robustness of our model results. Conclusion Epidemic modeling plays a critical role in planning and evaluating interventions for prevention. Simulation studies allow us to take into consideration available information on sexual network characteristics, such as mixing within and between communities as well as coverage levels for different prevention modalities in the combination prevention package.

Schistosomiasis in Malawi: a systematic review

IntroductionSchistosomiasis remains an important public health problem that undermines social and economic development in tropical regions of the world, mainly Sub-Saharan Africa. We are not aware of any systematic review of the literature of the epidemiology and transmission of schistosomiasis in Malawi since 1985. Therefore, we reviewed the current state of knowledge of schistosomiasis epidemiology and transmission in this country and identified knowledge gaps and relevant areas for future research and research governance.MethodsWe conducted computer-aided literature searches of Medline, SCOPUS and Google Scholar using the keywords: “schistosomiasis”, “Bilharzia”, “Bulinus” and “Biomphalaria” in combination with “Malawi”. These searches were supplemented by iterative reviews of reference lists for relevant publications in peer reviewed international scientific journals or other media. The recovered documents were reviewed for their year of publication, location of field or laboratory work, authorship characteristics, ethics review, funding sources as well as their findings regarding parasite and intermediate host species, environmental aspects, geographical distribution, seasonality of transmission, and infection prevalence and intensities.ReviewA total of 89 documents satisfied the inclusion criteria and were reviewed. Of these, 76 were published in international scientific journals, 68 were peer reviewed and 54 were original research studies. Most of the documents addressed urinary schistosomiasis and about two thirds of them dealt with the definitive host. Few documents addressed the parasites and the intermediate hosts. While urinary schistosomiasis occurs in most parts of Malawi, intestinal schistosomiasis mainly occurs in the central and southern highlands, Likoma Island and Lower Shire. Studies in selected communities estimated prevalence rates of up to 94.9% for Schistosoma haematobium and up to 67.0% for Schistosoma mansoni with considerable geographical variation. The main intermediate host species are Bulinus globosus and Bulinus nyassanus for urinary schistosomiasis and Biomphalaria pfeifferi for intestinal schistosomiasis. Seasonality of transmission tends to vary according to geographical, environmental, biological and behavioural factors.ConclusionTransmission of schistosomiasis in Malawi appears to be highly focal, with considerable variation in space and time. Many locations have not been covered by epidemiological investigations and, thus, information on the transmission of schistosomiasis in Malawi remains fragmented. Functional infection risk assessment systems based on systematic investigations and surveillance are required for developing informed prevention and control strategies.

Transmission of HIV in sexual networks in sub-Saharan Africa and Europe

We are reviewing the literature regarding sexual networks and HIV transmission in sub-Saharan Africa and Europe. On Likoma Island in Malawi, a sexual network was reconstructed using a sociometric survey in which individuals named their sexual partners. The sexual network identified one giant component including half of all sexually active individuals. More than 25% of respondents were linked through independent chains of sexual relations. HIV was more common in the sparser regions of the network due to over-representation of groups with higher HIV prevalence. A study from KwaZulu-Natal in South-Africa collected egocentric data about sexual partners and found that new infections in women in a particular area was associated with the number of life-time partners in men. Data about sexual networks and HIV transmission are not reported in Europe. It is, however, found that the annual number of sexual partners follows a scale-free network. Phylogenetic studies that determine genetic relatedness between HIV isolates obtained from infected individuals, found that patients in the early stages of infections explain a high number of new infections. In conclusion, the limited information that is available suggest that sexual networks play a role in spread of HIV. Obtaining more information about sexual networks can be of benefit for modeling studies on HIV transmission and prevention.

Descriptions of five new species of Metriaclima (Teleostei: Cichlidae) from Lake Malaŵi, Africa.

Lake Malaŵi is known for its endemic haplochromine species flock, most notably the rock-dwelling cichlids known as mbuna. One of the larger genera of mbuna is Metriaclima, a group consisting of 31 described species (including the five described herein) and approximately 45 recognized unique populations. Metriaclima is diagnosed by its feeding behavior and several morphological characteristics including the angle of the vomer and the presence of bicuspid teeth in the outer row of both the upper and lower jaws. Metriaclima zebra, the type species for the genus, was described based on a single specimen. While the collection location of this holotype is not known, based on the travel records of its collector, it is likely that the specimen originated from Likoma Island. The holotype was therefore compared to specimens from several localities around this island and was found to be morphologically indistinguishable from some of these. This study includes the morphological analysis of 496 specimens of Metriaclima belonging to 31 collections from Lake Malaŵi. Morphometric differences were analyzed and the relationships among several distinguishable populations of Metriaclima zebra were investigated. Our study further resulted in the description of the following five new species belonging to the M. zebra species complex: M. pambazuko, M. lundoense, M. midomo, M. tarakiki, and M. nigrodorsalis. These species were distinguished and described based on color patterns, morphometric, meristic, and ecological differences. These new species were compared with and distinguished from nearby populations of Metriaclima having similar pigmentation patterns and/or similar ecological niches. An artificial dichotomous key to the described species of Metriaclima is presented.

Genetic differentiation and diversity of Adansonia digitata L (baobab) in Malawi using microsatellite markers

Baobab (Adansonia digitata L) belonging to Bombacaceae family, is one of the most widely used indigenous priority tree species in sub-Saharan Africa, valued in the cosmetic industry for its seed oil, and powdery fruit pulp for juice making. Baobab has high potential for domestication in southern Africa, therefore understanding its genetic diversity and population structuring is warranted. The study investigated the level of genetic diversity and differentiation of five populations of A. digitata L. sampled from four diverse silvicultural zones in Malawi. Variation at nine microsatellite loci were examined in 150 individual trees. Low mean genetic diversity was expressed through genetic diversity indices: Nei’s genetic diversity (h, 0.18 ± 0.03), Shannon Information Index (I, 0.21 ± 0.07), observed number of alleles (na, 1.47 ± 0.10), effective number of alleles (ne, 1.23 ± 0.04) and percentage polymorphic loci (pp, 48 %). The low genetic variation found is attributed to the population growing in marginal areas of genetic centre of diversity of the species, anthropogenic factors and founder effects. Moderate genetic differentiation was observed among populations (Gst = 0.13) indicating the presence of a large number of common alleles resulting in a homogenisation effect. Clustering of individual trees by genetic similarity coefficients indicated that mainland trees were genetically closer than the trees on Likoma Island. Mantel’s test showed a weak positive insignificant correlation (Z = 0.12; P = 0.64) between genetic distance among populations and actual distance on the ground implying that geneflow was not directly influenced by isolation by distance. The results suggest that seed distribution and tree improvement should recognise the presence of ecotypes and conservation measures should protect all the populations due to existence of private alleles which are of adaptive importance.

Human leukocyte antigen class I haplotypes of human immunodeficiency virus–1–infected persons on Likoma Island, Malawi

Human leukocyte antigen (HLA) allele frequencies vary between different human populations, with implications both for the evolutionary pressures shaping those populations as well as for the outcome of new infectious epidemics. We defined HLA class I types in a well-described cohort of persons on Likoma Island in Malawi, a population for which there are lacking data on allelic frequencies. The profile of HLA frequencies was similar but phylogenetically distinct from those of other sub-Saharan African populations in neighboring regions. The most common A alleles included A30, A23, A28 (A*68), and A2, and the most common B alleles included B15 (group), B53, B58, and B44. Notably, the frequency of B53, which is protective against malaria, was similar to that of other malaria-endemic African countries, and higher than that in countries with less malaria. This is the first reported significant dataset of HLA class I allelic frequencies in Malawians.

The reliability of sexual partnership histories: implications for the measurement of partnership concurrency during surveys

To measure the reliability of sexual partnership histories collected during survey interviews and to assess the impact of measurement error on survey estimates of partnership concurrency. We used sociocentric data collected on Likoma Island (Malawi). Up to five of the respondents' most recent sexual partners were identified in population rosters. We assessed interpartner agreement (IPA) in reports of sexual partnerships (i.e. whether partners concordantly report that they have had sexual relations with each other) and its association with respondent and partnership characteristics. We estimated the extent of bias in the point prevalence of concurrency and the duration of overlap between concurrent partnerships according to two scenarios: one in which only partnerships reported by both partners were considered as 'true' ('concordant scenario'), and one in which partnerships reported by either partner were included ('complete scenario'). IPA was low in nonmarital relations, but was significantly higher in ongoing than in dissolved nonmarital relations. IPA was further associated with the number of other partners the respondents or their partner(s) had, as well as with the duration of ongoing partnerships. Biases in measurements of the prevalence of concurrent partnerships were large: concurrent partnerships were rare in the concordant scenario, but common in the complete scenario. This was particularly true among never married women. Estimates of the average duration of overlap between concurrent partnerships derived from self-reported survey data were also biased, particularly among married respondents. Future empirical tests of the 'concurrency hypothesis' and interventions targeting concurrent partnerships should take reporting biases into account.

Pyrethroid resistance in southern African Anopheles funestus extends to Likoma Island in Lake Malawi

BackgroundA mosquito survey was carried out on the island of Likoma in Lake Malawi with a view to collecting baseline data to determine the feasibility of implementing an integrated malaria vector control programme. No vector control interventions are currently being applied on the island apart from the sporadic use of treated and untreated bed nets.ResultsLarge numbers of Anopheles funestus were found resting inside houses. WHO susceptibility tests were carried out on wild caught females and 1-5 day old F-1 female progeny. Wild caught females were tested on deltamethrin (77.8% mortality) and bendiocarb (56.4% mortality). Female progeny were tested on deltamethrin (41.4% mortality), permethrin (40.4%), bendiocarb (52.5%), propoxur (7.4%), malathion, fenitrothion, DDT, dieldrin (all 100%) and pirimiphos-methyl (98.9%). The malaria parasite rate was 4.9%. A small number of Anopheles arabiensis were also collected.ConclusionThis locality is 1,500 km north of the currently known distribution of pyrethroid resistant An. funestus in southern Africa. The susceptibility results mirror those found in southern Mozambique and South African populations, but are markedly different to An. funestus populations in Uganda, indicating that the Malawi resistance has spread from the south.

Awareness of HIV/AIDS prevention and acceptance of HIV testing among residents in Likoma Island, northern Malawi

To evaluate the awareness of HIV/AIDS prevention education, and the acceptance of HIV testing among residents on Likoma Island, Malawi, a cross-sectional, population-based study of 579 residents aged > or =15 years from seven villages on Likoma Island was conducted during July and August 2007. Most of the subjects studied could correctly answer questions about their awareness of AIDS and knowledge of the ways to reduce HIV transmission. Moreover, the proportion of respondents (65.8%) who possessed complete knowledge of HIV/AIDS prevention was greater than the national average. By contrast, condom utilization was slightly lower. Our results also showed that a high proportion of respondents (70.3%) had been HIV tested at any time, 93.5% of them voluntarily. Among correlated factors, females [adjusted odds ratio (AOR)=1.7, 95% CI 1.1-1.6] and polygamous individuals (AOR=3.3, 95% CI 1.5-7.0) were more likely to receive an HIV test. Past experience of being HIV tested was a strong predictor of possessing good knowledge and attitudes towards HIV/AIDS prevention. We conclude that antiretroviral treatment provided by Likoma District Hospital has led to the successful scale-up of HIV testing in Likoma Island and consequently improved the awareness of HIV/AIDS. However, the use of condoms remains largely unsupported, and there is therefore still a need to intensify general HIV/AIDS education on the island.

HIV transmission networks

Over the past several years, one segment of the complex field of HIV transmission dynamics - heterosexual networks - has dominated theoretical and empirical investigation. This review provides an overview of recent work on HIV risks and networks, with a focus on recent findings in heterosexual network dynamics. Qualitative (ethnographic) assessments have demonstrated the heterogeneity and complexity of heterosexual connections, particularly in Africa, where tradition, official polygamy, and unofficial multiperson arrangements have lead to concurrency of sexual partnerships. A large, quantitative study on Likoma Island, Malawi, demonstrated the considerable, interlocking sexual connections that arise from a high-concurrency sexual setting, even with a low average number of partnerships (low degree) of long duration. Such settings, as suggested by ethnographic studies, may be common in Africa and, coupled with newer information about transmissibility during acute and early infection, may provide a plausible explanation for endemic transmission and possibly for rapid HIV propagation. Recognition of high-concurrency, low-degree networks is an important development for understanding HIV transmission dynamics. Their relevance to heterosexual transmission, and possible extension to other epidemiologic settings, reinforces the heterogeneity and complexity of HIV transmission dynamics.

The association of HIV serodiscordance and partnership concurrency in Likoma Island (Malawi)

Although the association of partnership concurrency and HIV prevalence has been studied in sub-Saharan settings, the impact of concurrency on HIV transmission has not. We investigated the association between concurrency and HIV serodiscordance in 142 ongoing marital and nonmarital relationships in which both partners were traced and tested for HIV. Our results suggest that multiple concurrent partnerships significantly increase exposure to HIV infection in the population of Likoma (Malawi). We highlight the potential role of behavioral interventions addressing partnership concurrency for HIV prevention.

Increasing uptake of HIV testing and counseling among the poorest in sub-Saharan countries through home-based service provision.

Uptake of HIV testing and counseling (HTC) is lower among members of the poorest households in sub-Saharan countries, thereby creating significant inequalities in access to HTC and possibly antiretroviral treatment. To measure uptake of home-based HTC and estimate HIV prevalence among members of the poorest households in a sub-Saharan population. Residents of 6 villages of Likoma Island (Malawi) aged 18-35 and their spouses were offered home-based HTC services. Socioeconomic status, HIV testing history, and HIV risk factors were assessed. Differences in HTC uptake and HIV infection rates between members of households in the lowest income quartile and the rest of the population were estimated using logistic regression. Members of households in the lowest income quartile were significantly less likely to have ever used facility-based HTC services than the rest of the population (odds ratio = 0.60, 95% confidence interval (CI): 0.36 to 0.97). In contrast, they were significantly more likely to use home-based HTC services provided during the study (adjusted odds ratio = 1.70, 95% CI: 1.04 to 2.79). Socioeconomic differences in uptake of home-based HTC were not due to underlying differences in socioeconomic characteristics or HIV risk factors. The prevalence of HIV was significantly lower among members of the poorest households tested during home-based HTC than among the rest of the population (adjusted odds ratio = 0.37, 95% CI: 0.14 to 0.96). HTC uptake was high during a home-based HTC campaign on Likoma Island, particularly among the poorest. Home-based HTC has the potential to significantly reduce existing socioeconomic gradients in HTC uptake and help mitigate the impact of AIDS on the most vulnerable households.

Disconnects in presumed heterosexual HIV transmission in Malawi

Obtaining large-scale sexual network data is difficult [1] and doing so in a poor country is especially difficult. We congratulate Helleringer and Kohler [2] on their pioneering study of a sexual network on Likoma Island, Malawi. Their approach represents an important step toward appropriate research designs for elucidating HIV transmission dynamics in sub-Saharan Africa. Despite this achievement, their results undermine their assertion that the Likoma sexual network sustains epidemic HIV transmission. In fact, their findings add to the already considerable evidence against penile–vaginal intercourse as the primary driver of HIV transmission in sub-Saharan Africa [3]. In moderate prevalence Likoma, Helleringer and Kohler observed an ‘apparently paradoxical distribution of HIV prevalence’. They found that persons in the core (bicomponents) of the main component of the sexual network were less likely to be HIV infected than those in peripheral positions in the main component or in small network components. This finding is at odds with prior empirical research, which indicates that, when significant HIV transmission occurs, persons located in the core of the corresponding risk network are more likely to be infected. In one high prevalence community, persons in the core of the injection and sexual network had considerably higher HIV prevalence and more frequent risk behaviors than those in peripheral or more isolated positions [4]. In that study, injection and homosexual risk behaviors were positively associated with prevalent HIV infection, but heterosexual risk behaviors were not. Similarly, among heterosexuals in a very low prevalence setting with little ongoing HIV transmission, infected persons were, with one exception, isolates, in small components, or on the periphery of the main component of the risk network [5,6]. In Likoma, it is surprising that self-reported symptoms of sexually transmitted infections (STI) are almost evenly distributed across the sexual network, and are not concentrated in the core as expected. Furthermore, no sexual risk variable (condom use, number of sex partners, STI symptoms, or age difference between sex partners) shows a meaningful association with prevalent HIV infection. Taken together, these observations suggest that the measured sexual network might not underlie HIV transmission in Likoma, and that other unmeasured blood and sexual exposures might be involved. To establish the primary modes of HIV transmission in sub-Saharan Africa with confidence, more appropriate research designs are required. Specifically, it is critical to assess blood and sexual exposures comprehensively (beyond just injections and vaginal intercourse) for incident cases and controls, trace their corresponding contacts and sequence-infected persons' HIV isolates [7–9].

Sexual network structure and the spread of HIV in Africa: evidence from Likoma Island, Malawi

Whereas sexual relationships among low-risk individuals account for the majority of HIV infections in sub-Saharan Africa, limited knowledge exists about the structure and characteristics of sexual networks among the general population in sub-Saharan Africa. To investigate the population-level structure of sexual networks connecting the young adult population of several villages on Likoma Island (Malawi), and analyse the structural position of HIV-positive individuals within the sexual network. A cross-sectional sociocentric survey of sexual partnerships and biomarkers of prevalent HIV infections. The study documents the existence of a large and robust sexual network linking a substantial fraction of the island's young adult population: half of all sexually active respondents were connected in a giant network component, and more than a quarter were linked through multiple independent chains of sexual relationships. This high network connectivity emerges within short time frames. The prevalence of HIV also varied significantly across the network, with sparser regions having a higher HIV prevalence than densely connected components. Several risk factors related to sexual mixing patterns help explain differentials in HIV prevalence across network locations. Contrary to claims that sexual networks in rural sub-Saharan Africa are too sparse to sustain generalized HIV epidemics, the structure of the networks observed in Likoma appears compatible with a broad diffusion of HIV among lower-risk groups. The non-homogeneous distribution of HIV infection within the network suggests that network characteristics are an important determinant of the dynamics of HIV spread within a population.

The Steamer Parish: The Rise and Fall of Missionary Medicine on an African Frontier

The Steamer Parish: The Rise and Fall of Missionary Medicine on an African Frontier. By Charles M. Good, Jr. University of Chicago Geography Research Paper, Number 244. Chicago and London: University of Chicago Press, 2004. Pp. xix, 487. $30.00 paper. The Steamer Parish adds to the growing literature on African medical missions by providing an innovative look at the way that technology shaped colonial and missionary society. In particular, Good explores the centrality of steam power and biomedicine to the Universities' Mission to Central Africa (UMCA) in colonial Nyasaland (now Malawi). The history of the making of this mission field (spanning from 1885 to 1964) is also a history of technological expansion. The first part of the book examines the initial encounters of UMCA missionaries and the subsequent growth of the Nyasaland Diocese. Steamship technology from Britain enabled the mission to establish a parish in a place where extensive overland travel was difficult, the threats of Ngoni raiders and Yao slavers were common, and negotiating the intersection of three different colonial administrations (British Nyasaland, Portuguese East Africa, and, before World War I, German East Africa) was complicated. Steamers offered a technological answer to the political, environmental, and social challenges of mission work in late nineteenth- and early twentieth-century Nyasaland. While providing a solution to certain on-the-ground obstacles of evangelization, the steamship also made its own demands on the missionaries, thereby creating new obstacles to be overcome. Steamships, for instance, required ports, firewood, and skilled workers. Reliance on steam technologies influenced myriad decisions, including the selection of Likoma Island for the mission headquarters. This choice turned the relatively small island midway between the north and south ends of Lake Malawi into a central site for mission activity and a common transit destination for those traveling up and down the lake. Steamships simulated and redirected various flows of people, thereby forging new social networks. In addition to enabling the movement of mission staff and Christian families, this newly imported technology came to play a part in the larger social and political history of the region; for example, by facilitating the initial part of the journey south for many men who sought work in southern Africa. After World War I, political conditions changed, and gradually, those problems that the steamer had been enlisted to solve (such as security) ceased to be pressing concerns. Even the very location of the headquarters came into question. Until Malawian independence, however, the mission continued to struggle under the weight of an institutional framework built on this earlier technological solution. The first half of The Steamer Parish situates the history of missionary medicine in Nyasaland within the broader social, political, technological, and environmental context of the UMCA mission. …