Differential immune responses in mice infected with the tissue-dwelling nematode Trichinella zimbabwensis.

To improve diagnostic tools, immunotherapies and vaccine development for trichinellosis surveillance and control there is a need to understand the host immune responses induced during infection with Trichinella zimbabwensis, a tissue-dwelling nematode. In this study, we sought to determine immune responses induced in mice during T. zimbabwensis infection. The parasite strain used (Code ISS1209) was derived from a naturally infected crocodile (Crocodylus niloticus) and is the main Trichinella species prevalent in southern Africa. Sixty 6- to 8-week-old female BALB/c mice were randomly assigned to two equal groups: T. zimbabwensis-infected (n= 30) and the non-infected control group (n= 30). Levels of serum tumour necrosis factor-alpha (TNF-α), interleukin-10 (IL-10), interleukin-4 (IL-4) as well as parasite-specific IgM, IgG, IgG1, IgG2a, IgG2b and IgG3 antibody responses were determined using enzyme-linked immunosorbent assay (ELISA). The cytokines and antibodies provided information on T-helper 1 (Th1)- and Th2-type, T-regulatory and antibody responses. Results showed that during the intestinal stage of infection, higher levels of parasite-specific IgM, IgG, IgG1 (P <  0.05) and IL-10 and TNF-α (P <  0.001) were observed in the Trichinella-infected group compared with the non-infected control group. In the parasite establishment and tissue migration phases, levels of IgG1 and IgG3 were elevated (P <  0.001), while those of IgM (P <  0.01) declined on days 21 and 35 post infection (pi) compared to the enteric phase. Our findings show that distinct differences in Th1- and Th2-type and T-regulatory responses are induced during the intestinal, tissue migration and larval establishment stages of T. zimbabwensis infection.

Comparison of praziquantel efficacy at 40 mg/kg and 60 mg/kg in treating Schistosoma haematobium infection among schoolchildren in the Ingwavuma area, KwaZulu-Natal, South Africa.

BACKGROUND: The World Health Organization recommends praziquantel (PZQ) (40 mg/kg body weight) for treating schistosomiasis. However, drug failure has been reported, prompting use of 60 mg/kg, for which results have been inconsistent. OBJECTIVES: To compare the efficacy of PZQ 40 mg/kg and 60 mg/kg in treating schoolchildren infected with Schistosoma haematobium. METHODS: The study was conducted during November 2017 - August 2018 in the Ingwavuma area, uMkhanyakude District, KwaZulu-Natal Province, South Africa. Children aged 10 - 15 years were screened for S. haematobium using a filtration technique. Infected children were randomly assigned to a dose of PZQ of 40 mg/kg or 60 mg/kg. Side-effects were recorded within 24 hours after treatment using questionnaires and direct observation. Four weeks after treatment, participants were retested for S. haematobium infection. Baseline and post-treatment mean egg counts were calculated. Cure rate (CR) and egg reduction rate (ERR) were used to determine PZQ efficacy, while repeated-measures analysis of variance determined the effect of both doses on infection intensity. A χ2 test was used to determine the association of side-effects with treatment, with a p-value ≤0.05. RESULTS: Forty-three and 36 children were treated with PZQ 40 mg/kg and 60 mg/kg, respectively. The 40 mg/kg group had a CR of 79.0% and an ERR of 97.2%, and the 60 mg/kg group a CR of 83.0% and an ERR of 98.3%. The effect of dose on infection intensity was not significantly different between the two groups (p>0.05). Abdominal pains, dizziness and fatigue were common among children who received PZQ 40 mg/kg, while headache, dizziness and nausea were common in the 60 mg/kg group. CONCLUSIONS: The efficacy of PZQ at 60 mg/kg was similar to that at 40 mg/kg. A dose >40 mg/kg therefore does not add value in treating S. haematobium infection. Transient side-effects (mostly dizziness) were observed more in the 60 mg/kg group than in the 40 mg/kg group. We recommend continued use of 40 mg/kg body weight for treating schistosomiasis.

Validation of a urine circulating cathodic antigen cassette test for detection of Schistosoma haematobiumin uMkhanyakude district of South Africa.

Circulating cathodic antigen (CCA) tests for schistosomiasis are fast and less complicated allowing making them good candidates for routine qualitative screening for schistosomiasis at point of care. The urine-CCA has been evaluated for detection of S. mansoni with promising results. Its specificity and consistency in detecting S. haematobium infection in different endemic regions has been variable. This study validated a rapid urine-CCA cassette test for qualitative detection of S. haematobium infection in an S. haematobium endemic area with low S. mansoni prevalence. Microscopic examination for the standard urine filtration technique was used to validate the commercially available urine-CCA cassette test (rapid medical diagnostics ®). The validation was done in a sample of primary school pupils (n = 420) aged 10-15 years in schools in the Jozini Municipality, KZN. There was a relationship between infection intensity and a positive urine-CCA test. Using the urine filtration method as the gold standard, the prevalence for S. haematobium was 40%, the accuracy of the CCA kit was 54.8%, sensitivity was 68.1% while the specificity was 45.8%. The positive predictive value was 45.82% while the negative predictive value was 68.05%. Both the urine filtration and the urine-CCA methods detected heavy (≥50 eggs/10 mL urine) and light infections at statistically significant levels. The overall accuracy, sensitivity and specificity of the urine-CCA cassette test were low. The urine-CCA cassette test performed much better for heavy infections than low infections (p < 0.05) implying that the kit may not be suitable for low endemic areas.

Memories of environmental change and local adaptations among molapo farming communities in the Okavango Delta, Botswana-A gender perspective.

This paper focuses on ways in which three riparian communities (Xobe, Shorobe and Tubu) practising flood recession (molapo) farming along the fringes of the Okavango Delta in Ngamiland District in north-western Botswana, present memories of experiential impacts of and adaptation to key environmental and anthropogenic change events. Participatory methodological tools were used to capture local knowledge of people who had resided in the Okavango wetlands for many years. Findings indicate that key environmental change events were characterized by intergenerational experiences of severe and frequent droughts, floods, and recurrent outbreaks of human and animal disease. These events had impacted livelihoods and well-being of communities. Community adaptation strategies were embedded in local institutions of governance, especially chieftainship and the Kgotla, as legitimate platforms for community re-organization against unpredictable environmental change. We concluded that policy/program formulation processes need to take cognisance of local communities' historical knowledge of environmental change and adaptation. In particular it emerged that men and women, and people of different ages have differentiated memories of historical events which are complementary and necessary in developing a comprehensive adaptation strategy.

An assessment of rural women's knowledge, constraints and perceptions on cervical cancer screening: the case of two districts in Zimbabwe.

This paper gives a sociological and anthropological insight into the rural women's perceptions and understanding of cervical symptomatology, screening and cancer. Qualitative data was collected through in-depth interviews and focus group discussions with women and health personnel. Quantitative data was obtained through questionnaires administered to 356 women from Mutoko and Shurugwi districts. The study revealed that cervical cancer is a disease that is of concern among health practitioners and women. 95.78% of the interviewed women had never gone for screening and had little knowledge about the various aspects of the disease in terms of causes, prevention and treatment. The study made four recommendations: the need for national screening policy and programme to be put in place, health education to women about cervical cancer, use of VIA in low resource settings and sensitisation of women about the availability of screening facilities in the districts where programmes are in place.

Characterization of an Indoor-Resting Population of Anopheles arabiensis (Diptera: Culicidae) and the Implications on Malaria Transmission in Tubu Village in Okavango Subdistrict, Botswana.

Comprehensive knowledge on vector dynamics is lacking in Botswana and yet essential for effective indoor residual spraying. This study assessed some of the entomological indices that contribute to malaria transmission by an indoor-resting population of Anopheles arabiensis Patton (Diptera: Culicidae) in Tubu village, Okavango subdistrict. The pyrethroid space-spray technique and hut searches were used to sample mosquitoes. Species and bloodmeal source identification were done using the polymerase chain reaction techniques. The infective status was determined by the enzyme-linked immuno-sorbent assay test. The human blood indices (HBI), human-biting rates (HBR), and vector densities were computed. Anopheles arabiensis was the sole vector and member of the Anopheles gambiae Giles complex identified. Significant changes in vector densities were observed over seasons, while nonsignificant differences were observed among the huts (P > 0.05). The main source of bloodmeal was cattle (46.8% [65]). There were no significant differences in HBI (P > 0.05) and HBR (P > 0.05) between the seasons. All the 271 mosquitoes tested for sporozoite infection were negative. The results showed that seasonal variations in vector densities corresponded to the traditional malaria and nonmalaria seasons. The vector population was relatively more zoophagic. The HBI and HBR were not influenced by the seasons. None of the endophilic mosquitoes tested (N = 271) was positive for sporozoites. Our study provided some relevant basic information to the local malaria control program that may be used to strategize their operations if malaria elimination has to be achieved by 2017.

Metabolic and adaptive immune responses induced in mice infected with tissue-dwelling nematode Trichinella zimbabwensis.

Tissue-dwelling helminths are known to induce intestinal and systemic inflammation accompanied with host compensatory mechanisms to counter balance nutritional and metabolic deficiencies. The metabolic and immune responses of the host depend on parasite species and tissues affected by the parasite. This study investigated metabolic and immuno-inflammatory responses of mice infected with tissue-dwelling larvae of Trichinella zimbabwensis and explored the relationship between infection, metabolic parameters and Th1/Th17 immune responses. Sixty (60) female BALB/c mice aged between 6 to 8 weeks old were randomly assigned into T. zimbabwensis-infected and control groups. Levels of Th1 (interferon-γ) and Th17 (interleukin-17) cytokines, insulin and blood glucose were determined as well as measurements of body weight, food and water intake. Results showed that during the enteric phase of infection, insulin and IFN-γ levels were significantly higher in the Trichinella infected group accompanied with a reduction in the trends of food intake and weight loss compared with the control group. During systemic larval migration, trends in food and water intake were significantly altered and this was attributed to compensatory feeding resulting in weight gain, reduced insulin levels and increased IL-17 levels. Larval migration also induced a Th1/Th17 derived inflammatory response. It was concluded that T. zimbabwensis alters metabolic parameters by instigating host compensatory feeding. Furthermore, we showed for the first time that non-encapsulated T. zimbabwensis parasite plays a role in immunomodulating host Th1/Th17 type responses during chronic infection.

Malaria and schistosomiasis risks associated with surface and sprinkler irrigation systems in Zimbabwe.

A comparative assessment of the malaria and schistosomiasis risks associated with surface and sprinkler irrigation systems in Zimbabwe was carried out. The risk assessment of the two diseases was done in accordance with the three standard components of health impact assessment, namely (i) community vulnerability, (ii) environmental receptivity, and (iii) capability of health services to respond to malaria and schistosomiasis. Records of the two diseases were obtained from four health centres serving two surface irrigation schemes and two sprinkler irrigation schemes. For comparison records were also obtained from health centres serving nearby dryland areas. Incidence of schistosomiasis as estimated from recorded new cases of the disease was much higher in surface irrigation schemes than in sprinkler irrigation schemes. For malaria it was the other way around. These findings were confirmed by rapid risk assessments. Malaria risk factors were more prominent in sprinkler irrigation schemes, whereas more schistosomiasis risk factors were identified in surface irrigation schemes. These observations were attributed to poorly maintained infrastructure and inadequate landscape-levelling, which created mosquito breeding sites within the fields in the case of sprinkler schemes, and to poor drainage structures, which created snail-breeding sites in the case of surface-irrigation schemes. Importantly, poor maintenance of sprinkler scheme infrastructure accounted for more disease promoting features than the engineering designs per se. This study demonstrated the value of complementing routinely collected health data with rapid assessment procedures for appraisal of commonly reported diseases.

Food selection behaviour of potential biological agents to control intermediate host snails of schistosomiasis: Sargochromis codringtoni and Tilapia rendalli.

The food selection behaviour of two fish species indigenous to Zimbabwe (Tilapia rendalli and Sargochromis codringtoni) was studied under laboratory conditions with a view to considering them as biological agents for snail control. Six glass aquaria were set up and divided into two sets each with two aquaria. One S. codringtoni was introduced into each aquarium of the first set while one T. rendalli was introduced into each aquarium of the other set. In one of the aquaria of each set the fish were supplied with snails and trout food. Snails and weeds were provided, but trout food was excluded in the second aquarium of each set while the third aquarium for each set was provided with trout food, snails and weeds. A fourth aquarium with weeds and snails but no fish was set up as a control. Data collected over 9 weeks showed that T. rendalli was primarily herbivorous while S. codringtoni was shown to be malacophagous. Presence of trout food made no difference in the snail-eating habit of S. codringtoni or the weed-eating behaviour of T. rendalli. However, trout food seemed to be a good protein supplement to T. rendalli as the fish with access to trout food gained more weight and length.

Prevalence and intensity of the schistosomiasis situation along the Zimbabwean urban and peri-urban shoreline of lake Kariba.

OBJECTIVE: To determine the prevalence and intensity of schistosomiasis in urban and peri-urban Kariba. DESIGN: A cross sectional schistosomiasis survey involving screening people for infection and searching for intermediate host snails. SETTING: Lake Kariba Research Station, Zimbabwe. SUBJECTS: One thousand and seventy three people living in four residential areas of Kariba were screened for both Schistosoma haematobium and Schistosoma mansoni. Seventeen water contact sites along the shoreline close to the residential areas were surveyed for snails. MAIN OUTCOME MEASURES: Prevalence and intensity of both S. haematobium and S. mansoni and abundance of intermediate host snails at potential transmission sites. RESULTS: The prevalence of S. haematobium and S. mansoni were 7.2% and 2.1% respectively. More males (8.4%) were infected with S. haematobium than females (5.7%). There was no difference in prevalence of S. mansoni between males (2.2%) and females (2.0%). Most infections of S. haematobium were in the age group of 15 to 19 years while the age distribution pattern for S. mansoni was patchy. Most of the infections detected were light i.e. one to 100 eggs per gram of faeces or less than 50 eggs per 10 ml of urine. Few intermediate host snails for schistosomiais were collected and none of them were infected with human schistosomes. CONCLUSION: Prevalence and intensity of schistosomiasis were low and therefore, the disease was not considered to be a major public health problem.

A preliminary assessment of the potential of the Muschovy duck (Cairina maschata) as a biocontrol agent of schistosomiasis intermediate host snails.

OBJECTIVE: To assess the impact of Muschovy ducks on snail populations. DESIGN: Populations of four different snail species were monitored in nine ponds for a period of 32 weeks. Zero, one and two ducks were randomly introduced to a set of three ponds in the 16th, 20th and 24th week. SETTING: Nine fenced ponds at De Beers Research Laboratory, Chiredzi. MAIN OUTCOME MEASURES: Reduction in snail population following introduction of ducks. RESULTS: Mean counts for the intervention period showed that more intermediate host snails (Bulinus globosus and Biomphalaria pfeifferi) were present in ponds where ducks were not introduced (control) than in ponds where either one or two ducks were introduced. In control ponds the mean counts for intermediate host snails were 1.37, 1.03 and 1.02 for control, treatment with one duck and treatment with two ducks respectively. Similar observations were made for Physa acuta, with mean counts of 1.10, 0.64 and 0.67 for control, treatment with one duck and treatment with two ducks, respectively. No differences were observed in snail counts of Melanoides turbeculata where 2.40 snails were collected from the control pond and 2.37 snails in both treatment ponds. There was no significant difference in number of snails in ponds with one or two ducks. CONCLUSION: The study demonstrated that Muschovy ducks significantly reduce snail populations in a pond environment. Further studies are required in large natural ponds before conclusive recommendations are made on the use of Muschovy ducks as biological control agents of schistosomiasis intermediate host snails can be drawn.

Successful control of schistosomiasis in large sugar irrigation estates of Zimbabwe.

OBJECTIVE: To assess the impact of schistosomiasis control activities in Hippo Valley Sugar Estates. DESIGN: A situation analysis of schistosomiasis control activities in Hippo Valley Estates was made. Snail and parasitology data collected over 13 and 21 years respectively was analysed to determine the impact of control activities. SETTING: Only data collected in Hippo Valley Sugar Estates was analysed. MAIN OUTCOME MEASURES: Reduction in prevalence of schistosomiasis and snail population densities. RESULTS: Prevalence of Schistosoma haematobium reduced from over 50% in 1980 to below 10% in 2000. Similarly, prevalence of S. mansoni reduced from 25% in 1980 to below 10% in 2000. Over the years, prevalences for both S. haematobium and S. mansoni fluctuated but showed a general decline. Snail numbers in water bodies within the estates fluctuated over the years, dropping from over 100,000 snails in 1986 to about 10,000 snails in 1998. The amount of niclosamid used to control snails varied over the years with less than 10 kg per year being used between 1995 and 1998. A marked improvement in safe water and sanitation facilities was noted. CONCLUSION: The significant reduction in prevalence and snail numbers suggests that the Hippo Valley Estates control programme has been successful. The success is attributed to chemotherapy and snail control supported by general improvement in safe water and sanitation facilities and health education.

Transmission of schistosomiasis in Kariba, Zimbabwe, and a cross-sectional comparison of schistosomiasis prevalences and intensities in the town with those in Siavonga in Zambia.

Given that the two communities lie only 10 km apart, on the northern shore of Lake Kariba, it is surprising that human schistosomiasis now appears to be a much less important health problem in Kariba town (Zimbabwe) than in Siavonga town (Zambia). In an attempt to explain this difference, the level and sites of Schistosoma haematobium and S. mansoni transmission in Kariba, and the prevalences and intensities of human infection with these parasites in both communities, have now been investigated. In a longitudinal study, a cohort of 378 schoolchildren, 150 subsistence fishermen and 42 commercial fishermen from Kariba town was screened three times for schistosome infection, at 6-month intervals. Sixteen human-water contact sites in or near the town were surveyed for intermediate host snails every month for 1 year. Finally, the results of screening 660 Kariba schoolchildren (in January 2001) and 527 Siavonga schoolchildren (in July 2002) were compared. In the longitudinal study, 9.0% of the schoolchildren, 7.3% of the subsistence fishermen and 0% of the commercial fishermen were each found positive for S. haematobium at least once. The corresponding values for S. mansoni were 2.5%, 12.5% and 26.3%, respectively. The results indicated that, each year in Kariba, 2.4% and 2.0% of schoolchildren and 18.2% and 5.2% of fishermen were infected with S. haematobium and S. mansoni, respectively. Although both Bulinus globosus and Biomphalaria pfeifferi were found at 14 of the 16 water-contact sites, snails infected with schistosomes that could infect mammals were only found at three of the sites. The problem of schistosomiasis in Kariba town appears to be greater among fishermen than schoolchildren, all transmission probably occurring in Lake Kariba. As expected, the overall prevalences of S. haematobium and S. mansoni infection among Siavonga schoolchildren (19.4% and 33.5%, respectively) were far higher than the corresponding values for Kariba schoolchildren (7.1% and 2.1%, respectively). The marked differences in the prevalence of human schistosomiasis between Kariba and Siavonga appear to be attributable to the better water and sanitation facilities and a history of schistosomiasis-control activities in Kariba town.

Laboratory experiments on snail predation by Sargochromis codringtoni, a candidate for biological control of the snails that transmit schistosomiasis.

The potential efficacy of Sargochromis codringtoni, a species of cichlid fish, in the biological control of snails carrying the Schistosoma spp. infecting man has long been recognized. A laboratory study to produce much-needed data on the malacophagous characteristics of this fish was conducted, to see if field studies on its possible role as a biological agent for snail control in Zimbabwe were likely to be worthwhile. The fish can consume large numbers of snails within a short period: a single fish, provided with trout pellets as an alternative food, not only chose to eat the snails but also consumed > 800 within 3 weeks. Addition of macrophytes to the aquaria used appeared to offer the snails no protection from predation. For fish measuring 15-18 cm in length, there was no size preference among snails measuring up to 12 mm in shell height nor was any species preference observed in experiments involving Bulinus globosus, B. tropicus and Melanoides tuberculata. The fish crushed B. globosus which were > 3.0 mm in shell height in their pharynges but swallowed smaller snails of this species whole. Before field trials are conducted, further laboratory studies, in which field conditions are simulated, should be carried out.