Dry Season Survey Research Articles

DRY SEASON SURVEY ON ABUNDANCE AND DISTRIBUTION OF IXODID TICKS IN CATTLE IN AUYO LOCAL GOVERNMENT AREA OF JIGAWA STATE, NIGERIA

Dry season survey on ticks was conducted to determine the genera, prevalence and distribution in various breeds of cattle in Auyo Local Government Area of Jigawa State, Nigeria. A total of 258 cattle were examined, out of which 51(19.8%) were males and 207(80.2%) females. An overall prevalence of 58.9% was recorded in all cattle examined. One hundred and seventy three ticks of three genera belonging to the family ixodidac were collected and identified of which Red Bororo recorded 65(37.6%), crossbreeds had 41(23.7%), White Fulani had 40(37.6%) while Sokoto gudali had 27 (15.6%). Of the tick genera identified, their prevalence showed, Amblyomma spp 87(50.3%) as the commonest, followed by Boophilus spp 69 (39.9%) and Hyalomma spp 17(9.8%). Distribution of ticks infestation by sex was significantly higher (P<0.05) in males 38(74.5%) then in females 114(55.1%). Tick infestation was significantly (P<0.05) higher in adults 115(65.3%) than in calves 37(57.2%). Dunkan Fulani recorded highest revalence 89(70.6%) of tick infestation by location.

Nocturnal surveys of lined seahorses reveal increased densities and seasonal recruitment patterns.

Although the nighttime ecology of organisms remains understudied, nocturnal surveys play an integral part in assessing fish assemblages and the selective forces shaping them. Eleuthera (Bahamas) contains an unusual population of lined seahorses (Hippocampus erectus) in an anchialine lake, possessing morphological characteristics distinct from those found in the ocean. Population surveys for seahorses and their potential predators were conducted at midnight and midday during wet and dry seasons, with belt transects perpendicular to the shoreline that increased in depth away from shore. Nocturnal surveys uncovered seahorse densities 259% higher than daytime transects on average. Sex ratios were consistently male-biased, and the frequency of animals from different reproductive categories varied significantly by time of day, with gravid males observed around the clock but females and nongravid males observed more often at night. Spatial and seasonal recruitment was detected for the first time in this species, with an increase in juveniles detected in the shallow ends of transects during dry season surveys. Juvenile recruitment is poorly understood across syngnathid fishes, so the detection of early recruits at night has broad implications for this fish family. Seahorses from all reproductive categories were perched significantly higher in the water column during the night regardless of their depth or season. Predator densities followed a similar pattern with higher densities observed at night, indicating that elevated nocturnal perch height may be a response to predator presence. However, the selective agents driving these nocturnal behaviors have yet to be identified. Considering H.erectus is listed on the IUCN Red List as "Vulnerable," the increase in nocturnal population size and the detection of juveniles has crucial implications for understanding their ecology, recruitment, and conservation.

Quasi-3D mapping of soil moisture in agricultural fields using electrical conductivity sensing

Knowledge of real time spatial distribution of soil moisture has great potential to improve yield and profit in agricultural systems. Recent advances in non-invasive electromagnetic induction (EMI) techniques have created an opportunity to determine soil moisture content with high-resolution and minimal soil intrusion. So far, EMI has mainly been used for homogenous soil conditions, which are not common in agriculture and results are mainly validated by excavated pits or calibration models using soil samples on a transect. This study converts apparent electrical conductivity data recorded with a Dualem-1Hs EM-metre for two surveys of variable moisture conditions (dry and wet season) with 2475 and 2174 data points over 5.4 ha, in a field with a contrasting vertical soil profile into spatiotemporal management zones. A least square inversion algorithm was used to determine electrical conductivities for individual soil layers of 0–0.5 m, 0.5–0.8 m and 0.8–1.6 m. Soil samples from the depth of 0.5 m and 0.8 m were used for soil moisture calibrations. A laboratory experiment under controlled conditions developed electric conductivity vs volumetric water content relations with power law functions for required soil depth slices with R2 values between 0.98 and 0.99. Subsequently, EMI data were converted to volumetric water contents for each layer and predictions were spatially displayed. Median change between the measured apparent conductivity and inverted values range from 6 to 17 mS m-1 resulting in 3–7% difference in volumetric water prediction. These EMI based soil moisture predictions were compared with neutron moisture metre measurements, with Pearson R values of 0.74 and 0.95 for the wet and dry season surveys, respectively. The method is robust and offers a comparatively fast method to estimate the soil moisture status in fields and subsequently make informed management decisions.

The prevalence of scabies, pyoderma and other communicable dermatoses in the Bijagos Archipelago, Guinea-Bissau.

IntroductionSkin diseases represent a significant public health problem in most low and middle income settings. Nevertheless, there is a relative paucity of high-quality epidemiological data on the prevalence of these conditions.Materials/MethodsWe conducted two cross-sectional population-based skin-surveys of children (6 months to 9 years old) in the Bijagós Archipelago of Guinea-Bissau during the dry season (February-March 2018) and the wet season (June-July 2018). Following a period of training, a nurse performed a standardised examination for communicable dermatoses for each participant. We calculated the prevalence of each skin condition and investigated demographic associations.Results1062 children were enrolled in the dry season survey of whom 318 (29.9%) had at least one skin diseases. The most common diagnosis was tinea capitis (154/1062, 14.5% - 95% CI 12.5–16.8%) followed by tinea corporis (84/1062, 7.9% - 95% CI 6.4–9.7%), pyoderma (82/1062, 7.7% - 95% CI 6.2–9.5%) and scabies (56/1062. 5.2% - 95%CI 4.0–6.8%). 320 children were enrolled in the wet season survey of whom 121 (37.8%) had at least one skin problem. Tinea capitis remained the most common diagnosis (79/320, 24.7% - 95% CI 20.1–29.9%), followed by pyoderma (38/320, 11.9% - 95% CI 8.6–16.1%), tinea corporis (23/320, 7.2% - 95% 4.7–10.7%) and scabies (6/320, 1.9% - 95% CI 0.8–4.2%).ConclusionsOur study, which utilised robust population-based cluster random sampling methodology, demonstrates the substantial disease burden caused by common communicable dermatoses in this setting. Given these findings, there is a need to consider common dermatoses as part of Universal Health Coverage to deliver ‘skin-health for all’.

Environmental Emergency: Why Did the False Mussel Mytilopsis sallei Not Invade Darwin Harbour, Australia?

No introduced marine pests, also known as invasive marine species, were detected in a dry season survey in August 1998 in Darwin Harbour, Northern Territory, Australia. A postwet-season survey in March 1999 found extensive populations of the false mussel Mytilopsis sallei (Recluz, 1849) in the Cullen Bay Marina. An environmental emergency was declared and M. sallei were eliminated. The present paper examines possible reasons for the failure of M. sallei to establish outside Cullen Bay. Mytilopsis sallei is a fresh/brackish water species that naturally lives in low salinities. It is hypothesized that the osmotic shock of rapid movement from low salinity water in Cullen Bay to much higher salinities outside the marina killed the veligers when they were discharged through the entrance lock when it was opened to allow vessel movements. If it entered the harbour, M. sallei could possibly have established in low salinity water in the arms leading into the harbour and possibly have spread in northern Australia.

School-based malaria prevalence: informative systematic surveillance measure to assess epidemiological impact of malaria control interventions in the Democratic Republic of the Congo

BackgroundIn southern Democratic Republic of the Congo, malaria transmission is stable with seasonal fluctuations. Different measurements can be used to monitor disease burden and estimate the performance of control programmes. Repeated school-based malaria prevalence surveys (SMPS) were conducted from 2007 to 2014 to generate up-to-date surveillance data and evaluate the impact of an integrated vector control programme.MethodsBiannual SMPS used a stratified, randomized and proportional sampling method. Schools were randomly selected from the entire pool of facilities within each Health Area (HA). Subsequently, school-children from 6 to 12 years of age were randomly selected in a proportional manner. Initial point-of-care malaria diagnosis was made using a rapid detection test. A matching stained blood film was later examined by expert microscopy and used in the final analysis. Data was stratified and analysed based on age, survey time and location.ResultsThe baseline SMPS (pre-control in 2007) prevalence was approximately 77%. From 2009 to 2014, 11,628 school-children were randomly screened. The mean age was 8.7 years with a near equal sex ratio. After exclusion, analysis of 10,493 students showed an overall malaria prevalence ratio of 1.92 in rural compared to urbanized areas. The distribution of Plasmodium falciparum malaria was significantly different between rural and urban HAs and between end of wet season and end of dry season surveys. The combined prevalence of single P. falciparum, Plasmodium malariae and Plasmodium ovale infections were 29.9, 1.8 and 0.3% of those examined, respectively. Only 1.8% were mixed Plasmodium species infections. From all microscopically detected infections (3545 of 10,493 samples examined), P. falciparum represented 88.5%, followed by P. malariae (5.4%) and P. ovale (0.8%). Cases with multiple species represented 5.3% of patent infections. Malaria prevalence was independent of age and gender. Control programme performance contributed to a significant decrease in mean P. falciparum infection density in urban compared to rural locations. Some rural areas remained highly refractory to control measures (insecticide-treated bed nets, periodic indoor residual spraying).ConclusionThe SMPS is a useful longitudinal measurement for estimating population malaria prevalence and demonstrating disease burden and impact of control interventions. SMPS can identify refractory areas of transmission and thus prioritize control strategies accordingly.

Storage rot fungi and seed-borne pathogens of onion

Surveys of fungi associated with postharvest deterioration of onion bulbs in four major markets in Kumasi Metropolis of the Ashanti Region of Ghana were conducted. Rotten onion bulbs obtained from the four markets (Abinchi, Anloga, Kwadaso and Central markets) were infected by five fungal species: Aspergillus niger , A. flavus, Penicillium sp., Rhizopus stolonifer and Fusarium oxysporum . Of these, A. niger and Penicillium sp. were the most frequently isolated fungi. A. flavus was the least encountered fungus. R. stolonifer and A. niger were the most pathogenic. Black mould, blue mould, soft rot, neck rot and basal plate rot were the major storage rots identified in a dry season survey in the markets. Incidences of these storage rots were higher in the wet season. Black mould enjoyed the highest incidence in all markets. Using the moist blotter method as recommended by the International Seed Testing Association (ISTA), seed-borne mycoflora of 37 samples of farmer-saved onion seeds from Bawku in the Upper East Region of Ghana were also examined. Nine different fungal species were identified and isolated from the seeds viz. A. niger, A. flavus, Penicillium sp., R. stolonifer, Fusarium oxysporum, Fusarium verticilloides, Fusarium poae, Alternaria porri and Botrytis sp. The most frequently encountered fungi were A. niger, R. stolonifer, A. flavus, Penicillium sp. and F. verticilloides with the occurrence of 33.3, 32.5, 25.8, 3.1 and 3.0%, respectively. The postharvest disease with the highest incidence in all the four markets surveyed was black mould. Some seed-borne fungi of onion were found to be associated with the onion bulb rots. Therefore, infected onion seeds could serve as inoculum source of the postharvest diseases of onion and contribute to the rot of bulbs during storage. In general, practices such as rotation, sanitation, optimum fertilization, preventive chemical applications, harvest timing and proper handling, harvesting, and storage are recommended for onion disease management. Keywords : Post-harvest, seed-borne, mycoflora, pathogenic, fungi

Dry season survey of aspergilli in the air of Benin City, Nigeria

In both indoor survey of the air over Benin, eleven species of <i>Aspergillus</i> were commonly found. There were more species in the air in January than in February and March. The spore concentration of these species in the air was found to be associated with the environmental condition, vegetation and human activities of each area of the city sampted. Most of them showed a consistent diurnal pattern while others were inconsistent. However <i>A. versicolor</i> and <i>A. tamarii</i> exhibited double peak patterns. Among the substrates used in trapping these fungi, yam recorded the highest number of <i>Aspergiltus</i> species (II).

Absence of dry season Plasmodium parasitaemia, but high rates of reported acute respiratory infection and diarrhoea in preschool-aged children in Kaédi, southern Mauritania

BackgroundThe epidemiology of malaria in the Senegal River Gorgol valley, southern Mauritania, requires particular attention in the face of ongoing and predicted environmental and climate changes. While “malaria cases” are reported in health facilities throughout the year, past and current climatic and ecological conditions do not favour transmission in the dry season (lack of rainfall and very high temperatures). Moreover, entomological investigations in neighbouring regions point to an absence of malaria transmission in mosquito vectors in the dry season. Because the clinical signs of malaria are non-specific and overlap with those of other diseases (e.g. acute respiratory infections and diarrhoea), new research is needed to better understand malaria transmission patterns in this region to improve adaptive, preventive and curative measures.MethodsWe conducted a multipurpose cross-sectional survey in the city of Kaédi in April 2011 (dry season), assessing three major disease patterns, including malaria. Plasmodium spp. parasite rates were tested among children aged 6–59 months who were recruited from a random selection of households using a rapid diagnostic test and microscopic examination of Giemsa-stained thick and thin blood films. Acute respiratory infection and diarrhoea were the two other diseases investigated, administering a parental questionnaire to determine the reported prevalence among participating children.FindingsNo Plasmodium infection was found in any of the 371 surveyed preschool-aged children using two different diagnostic methods. Acute respiratory infections and diarrhoea were reported in 43.4% and 35.0% of the participants, respectively. About two thirds of the children with acute respiratory infections and diarrhoea required medical follow-up by a health worker.ConclusionsMalaria was absent in the present dry season survey in the capital of the Gorgol valley of Mauritania, while acute respiratory infections and diarrhea were highly prevalent. Surveys should be repeated towards the end of rainy season, which will enhance our understanding of the potential changes in malaria transmission in a region known as ‘hot spot’ of predicted climate change.

Species composition, relative abundance and habitat association of small mammals along the altitudinal gradient of Jiren Mountain, Jimma, Ethiopia

AbstractTo document the species composition, relative abundance and habitat association of small mammals, wet and dry season surveys were conducted along the altitudinal gradient of Jiren Mountain, Jimma area, Ethiopia. Sherman traps were used to capture small mammals from the six habitats: wetland, mixed plantation, open shrub, eucalyptus plantation, montane grassland and coffee plantation. The 393 trap nights, from the six habitat types, yielded 106 individual small mammals of tweleve species. The trapped rodents were Lophuromys flavopunctatus, Stenocephalemys albipes, Desmomys harringtoni, Mus mahomet, Lemniscomys barbarous, L. striatus, Tachyoryctes splendens, Mastomys natalensis and the insectivores Crocidura fumosa and C. turba. Two species of rodents Hystrix cristata and Helioscuirus gambianus were observed. Lophuromys flavopunctatus and S. albipes contributed 83.8% of the total capture. L. flavopunctatus, S. albipes and D. harringtoni were distributed in all habitats and gradients. T. splendens was captured from montane habitat, while the zebra mice were associated with the lower altitude habitats. Lophuromys flavopunctatus and M. natalensis extended their range deep into the coffee plantation habitats. Uncontrolled vegetation exploitation of the mountains for timber production and fire wood collection are the major threats. Conservation of the area to reduce the anthropogenic pressure is essential.

Highly debilitating natural Trypanosoma vivax infections in Brazilian calves: epidemiology, pathology, and probable transplacental transmission

Clinical, epidemiological, and pathological aspects of trypanosomiasis caused by Trypanosoma vivax in calves were reported for the first time in northeast Brazil. Clinical and epidemiological data, packed cell volumes (PCV), and parasitemia were assessed in 150 calves in May 2009 (rainy season-survey 1) and in 153 calves in November 2009 (dry season-survey 2) in three farms (A, B, and C). Prevalence of T. vivax in calves examined in the survey 1 was 63.3%, 65.0%, and 80.0% in farms A, B, and C, respectively. Morbidity varied from 63.3% to 80%, mortality from 15% to 30% and lethality from 23% to 37.5%. In survey 1, for all farms, high parasitemia (from 30.3 to 26.2 × 10(6) parasites/mL), fever (from 39.8 to 40.3°C), low PCV (from 15.7% to 18.1%), and body score (from 2.5 to 3.5) were detected. Calves showed depression, weight loss, pale mucous membranes, enlarged lymph nodes, edema of the dewlap, cough, coryza, and diarrhea. The animals from farms A and B were treated with diminazene aceturate. Six months after, in survey 2, non-treated calves from farm C showed values for prevalence (81.82), morbidity (81.82), mortality (12.73), and lethality (15.55) similar to those in survey 1 (P > 0.05). Also in survey 2, four calves aging merely 1-3days old presented high parasitemia levels (from 32 × 10(6) to 74 × 10(6) parasites/mL), suggesting transplacental transmission. In conclusion, trypanosomiasis by T. vivax constitutes high prevalent disease for calves raised in Brazilian semiarid and may have transplacental transmission.

Spatial dispersion and characterisation of mosquito breeding habitats in urban vegetable-production areas of Abidjan, Côte d'Ivoire

Although urban agriculture (UA) in the developing world may enhance nutrition and local economies, it may also lead to higher densities of mosquito breeding sites and, consequently, to increased transmission of malarial parasites. If targeted interventions against malaria vectors are to be successful in urban areas, the habitats that support Anopheles breeding need to be identified and detected. Mosquito breeding sites have recently been characterised, and the factors associated with productive Anopheles habitats identified, in market gardens of Abidjan, Côte d'Ivoire. Two surveys were conducted in seven vegetable-production areas, one towards the end of the rainy season and one during the dry season. A standardized methodology was used for habitat characterisation and the detection of Anopheles larvae and mosquito pupae. Overall, 454 and 559 potential mosquito-breeding sites were recorded in the rainy-season and dry-season surveys, respectively. In the rainy season, Anopheles larvae and mosquito pupae were found in 29.7% and 5.5% of the potential breeding sites, respectively, whereas the corresponding percentages in the dry season were 24.3% and 8.6%. The potential breeding sites in an agricultural zone on the periphery of Abidjan were those least likely to be positive for Anopheles larvae and mosquito pupae whereas 'agricultural trenches' between seedbeds were the sites most likely to be positive. In a spatially-explicit Bayesian multivariate logistic-regression model, although one out of every five such wells was also found to harbour Anopheles larvae, irrigation wells were found to be the least productive habitats, of those sampled, for pupae. In the study area, simple and cost-effective strategies of larval control should be targeted at agricultural trenches, ideally with the active involvement of local stakeholders (i.e. urban farmers and urban agricultural extension services).

Dry Season Production of Filariasis and Dengue Vectors in American Samoa and Comparison with Wet Season Production

Aedes polynesiensis and Ae. aegypti breeding site productivity in two American Samoa villages were analyzed during a dry season survey and compared with a wet season survey. Both surveys identified similar container types producing greater numbers of pupae, with buckets, drums, and tires responsible for > 50% of Aedes pupae during the dry season. The prevalence of containers with Ae. polynesiensis and the density of Ae. polynesiensis in discarded appliances, drums, and discarded plastic ice cream containers were significantly greater during the dry season. Aedes aegypti pupal densities were significantly greater in the dry season in ice cream containers and tires. Significant clustering of the most productive container types by household was only found for appliances. The high productivity for Ae. polynesiensis and Ae. aegypti pupae during the wet and dry seasons suggests that dengue and lymphatic filariasis transmission can occur throughout the year, consistent with the reporting of dengue cases.

Elephants caught in the middle: impacts of war, fences and people on elephant distribution and abundance in the Caprivi Strip, Namibia

AbstractWe conducted wet [26 March–4 April 2003 (Apr03)] and dry [1–8 November 2005 (Nov05)] season aerial surveys of African elephants (Loxodonta africanaBlumenbach) in the Caprivi Strip, Namibia to provide an updated status report on elephant numbers and distribution and assist with a historical analysis of elephant distribution and abundance in the Caprivi Strip. During the wet season when water was available in seasonal pans, elephants were widely distributed throughout the survey area. In contrast, during the dry season, a majority of elephant herds occurred within 30 km of the perennial Kwando, Linyanti and Okavango rivers and few herds occurred within the West Caprivi Game Reserve where water in the seasonal pans was limited. We estimated 5318 elephants for the 7731‐km2survey area (0.71 elephants km−2) for the Apr03 wet season survey and 6474 elephants for the 8597‐km2survey area (0.75 elephants km−2) for the Nov05 dry season survey. Based on our aerial surveys and reports of elephant numbers and distribution from historical aerial surveys and telemetry studies, civil war, veterinary fences and human activities appear to have effected changes in African elephant abundance, distribution and movements in the Caprivi Strip, Namibia since 1988 when the first comprehensive aerial surveys were conducted.

Prevalence and risk factors of hookworm-related cutaneous larva migrans in a rural community in Brazil

The epidemiology of hookworm-related cutaneous larva migrans (HrCLM) in endemic communities is not well understood. To describe the prevalence of HrCLM and to identify environmental and behavioural risk factors for the infestation, two cross-sectional surveys were conducted in a small village in an endemic area of north-eastern Brazil - one in the rainy season and the other in the dry season. The members of each household were examined clinically for the presence of HrCLM, and information on possible risk factors was collected. HrCLM, which was diagnosed in 45 individuals in the rainy-season survey and in 17 in the dry-season survey, was significantly more prevalent in the rainy season (4.4% v. 1.7%; P<0.001). The age-specific prevalences peaked, at 14.9%, in infants and children aged < or = 4 years. In a logistic regression analysis, the independent risk factors for current infestation or infestation in the preceding 6 months were identified as young age (odds ratio = 0.96; 95% confidence interval = 0.94-0.98), living in a house without a solid floor (odds ratio = 1.99; 95% confidence interval = 1.22-3.23), and walking barefoot (odds ratio = 1.77; 95% confidence interval = 1.12-2.80). In the study area, therefore, HrCLM is a common parasitic skin disease in children, is associated with behavioural and environmental risk factors, and shows marked seasonality in its prevalence. Local control of HrCLM should be based primarily on the health education of mothers and the elder girls who take care of their younger siblings.

Sources of organic matter in sediments from the Ord River in tropical northern Australia

The sources of organic matter in the sediments from the Ord River and estuary were assessed using stable carbon isotope values (δ 13C), lipid biomarkers and distributions of chlorophylls and carotenoids as part of a larger multidisciplinary study examining the biogeochemistry of this tropical, macrotidal and large scale estuary. Two field trips were undertaken to obtain samples from both the dry (September, 2002) and wet (February, 2003) seasons. Both biomarker and stable isotope data indicate predominant contributions of organic material from the surrounding vegetation. However, the character of the terrestrial organic matter changes from the freshwater to the marine sections of the river. The sterol profiles in the freshwater sediments are relatively simple and dominated by the C 29 sterols 24-ethylcholest-5-en-3β-ol (sitosterol) and 24-ethylcholesta-5,22E-dien-3β-ol (stigmasterol) with small quantities of 24-methylcholest-5-en-3β-ol (campesterol), all of which are common sterols in higher plants. In the dry season survey, triterpenoid alcohols were generally absent from the freshwater sediments, but in the wet season there was a small contribution from compounds such as α- and β-amyrin and lupeol, indicating additional higher plant input, possibly from further inland in the catchment. Within Cambridge Gulf and the Ord estuary, the waterways are fringed with mangroves which contribute substantial quantities of organic matter as shown by distinctive distributions of triterpenoid alcohols dominated by taraxerol. However, this is not the major triterpenoid in the mangrove trees studied, but seems to be considerably more stable to biodegradation and so dominates the triterpenoids found. Isotope, biomarker (fatty acids, phytol and sterols) and pigment data suggest that only a small part of the sedimentary organic matter is derived from microalgae. Contributions from diatoms (24-methylcholesta-5,22E-dien-3β-ol; fucoxanthin), green algae (Δ 7-sterols), cyanobacteria (C 32 hopanol; zeaxanthin) and dinoflagellates (dinosterol; peridinin) could be recognized. In this environment the high turbidity of the water column severely limits phytoplankton production, although productivity of microphytobenthos on the banks of the river can potentially be high.

RISK OF GIARDIA INTESTINALIS INFECTION IN CHILDREN FROM AN ARTIFICIALLY RECHARGED GROUNDWATER AREA IN MEXICO CITY

The objective of this study was to assess the risk of infection with Giardia intestinalis in children living in an area with artificial groundwater recharge and potable water reuse in Mexico City. Eligible wells and surrounding homesteads were defined by using a geographic information system. Five wells were tested for G. intestinalis cysts per 400 liters of water. A total of 750 eligible households were visited during two cross-sectional surveys. Stool samples were provided by 986 children in the rainy season study and 928 children during the dry season survey for parasitologic tests. Their guardians provided information on water, sanitation, hygiene, and socioeconomic variables. The prevalence rates of G. intestinalis infection were 9.4% in the rainy season and 4.4% in the dry season. Higher rates of infection were observed in older individuals (9.5% and 10.6%) and girls had a lower risk of infection than boys (odds ratio [OR] =0.55, 95% confidence interval [CI] = 0.34, 0.88 in the rainy season and OR = 0.47, 95% CI = 0.25, 0.90 in the dry season). During the wet season survey, a health risk was detected among those storing water in unprotected receptacles (OR = 4.00, 4.69, and 5.34 for those using uncovered jars, cisterns or tanks, and buckets, respectively), and bathing outside the dwelling, i.e., using a tap (OR = 1.93, 95% CI = 1.10, 3.39). A health risk was also detected among children from households with unsafe food hygiene practices (OR =2.41, 95% CI =1.10, 5.30) and those with no hand-washing habits (OR = 2.27, 95% CI = 1.00, 5.20). Groundwater reserves are at risk of fecal pollution, as indicated by the presence of G. intestinalis cysts. However, the endemic pattern of intestinal infection reflects low standards of personal hygiene and unsafe drinking water storage and food-related practices at household level. Prevention activities must address health education and environmental protection policies.

Markets, ethnicity and environment in a vulnerable landscape: the case of small‐scale vegetable production on the Jos Plateau, Nigeria, 1991–2001

This paper explores changing socio‐environmental interactions in the vegetable producing areas of the Jos Plateau over the decade 1991–2001. It considers the pressures of market forces and ethnic competition and the tensions which arise as interactions between the two are played out in a fragile physical, social and institutional environment. The region has seen a remarkable expansion in irrigated vegetable production, as dry season surveys in 1991 and 2001 attest. Local farmers appear extremely positive in their perceptions of change, pointing not only to expanded production, but also to other improvements, like growing percentages of children in school and improved transport. But behind this rosy view of change there are tensions and a series of unresolved questions which may soon have to be addressed. We examine the changing nature of socio‐environmental interactions over the decade and ask whether and how current levels of production can be sustained in the context of a currently largely unregulated production system and growing competition for land. Given the important role of the Plateau as a source of temperate fruit and vegetables in West Africa, these questions have significance far beyond the Plateau region itself.

Roof gutters: a key container for Aedes aegypti and Ochlerotatus notoscriptus (Diptera: Culicidae) in Australia.

The contribution of roof gutters to Aedes aegypti (L.) and Ochlerotatus notoscriptus (Skuse) pupal populations was quantified for the first time in Cairns, Australia. Concurrent yard and roof surveys yielded an estimated 6,934 mosquito pupae, comprising four species. Roof gutters were an uncommon but productive source of Ae. aegypti in both wet season (n = 11) and dry season (n = 2) surveys, producing 52.6% and 39.5% of the respective populations. First story gutters accounted for 92.3% of the positive gutters. Therefore, treatment of roof gutters is a critical element in Ae. aegypti control campaigns during dengue outbreaks. In wet season yards, the largest standing crops of Ae. aegypti occurred in garden accoutrements, discarded household items, and rubbish (36.4%, 28.0%, and 20.6%, respectively). In dry season yards, rubbish produced 79.6% of the Ae. aegypti pupae. The number of Ae. aegypti pupae/person was 2.36 and 0.59 for the wet and dry season surveys, respectively.

The risk of enteric infections associated with wastewater reuse: the effect of season and degree of storage of wastewater

The effect of season and wastewater storage on the risk of Ascaris lumbricoides infection and diarrhoeal disease associated with wastewater reuse was studied in Mexico in 1991. Data were collected from 10 489 individuals during a dry-season survey. Exposure was to untreated wastewater, or effluent from 1 reservoir (⩽1 nematode egg/L), or no wastewater irrigation (control group). The results were compared with a previous rainy-season survey which included effluent from 2 reservoirs in series. Direct exposure to untreated wastewater was associated with an excess risk of A. lumbricoides infection in children aged <5 years (OR = 18·0) and persons aged >5 years (OR = 13·5) and an increased risk of diarrhoea, particularly to children aged <5 years(OR = 1·75); effects were strongerin the drythanin the rainyseason. There was also an excess risk associated with the 1-reservoir group for A. lumbricoides infection (OR = 21·2 and 9·4) and for diarrhoeal disease (OR = 1·1 and 1·5) but little excess associated with the 2-reservoirs group. Therefore, wastewater retention in 1 reservoir (quality 10 5 faecal coliforms/100 mL, ⩽1 egg/L) does not significantly reduce risks of Ascaris infection and diarrhoeal disease whereas retention in 2 reservoirs in series (quality 10 3 faecal coliforms/100 mL, no detectable eggs/L) does.