Sentinel Communities Research Articles

Toward the definition of specific protection goals for the environmental risk assessment of chemicals: A perspective on environmental regulation in Europe.

This critical review examines the definition and implementation of environmental protection goals for chemicals in current European Union (EU) legislation, guidelines, and international agreements to which EU countries are party. The European chemical industry is highly regulated, and prospective environmental risk assessments (ERAs) are tailored for different classes of chemical, according to their specific hazards, uses, and environmental exposure profiles. However, environmental protection goals are often highly generic, requiring the prevention of "unacceptable" or "adverse" impacts on "biodiversity" and "ecosystems" or the "environment as a whole." This review aims to highlight working examples, challenges, solutions, and best practices for defining specific protection goals (SPGs), which are seen to be essential for refining and improving ERA. Specific protection goals hinge on discerning acceptable versus unacceptable adverse effects on the key attributes of relevant, sensitive ecological entities (ranging from organisms to ecosystems). Some isolated examples of SPGs for terrestrial and aquatic biota can be found in prospective ERA guidance for plant protection products (PPPs). However, SPGs are generally limited to environmental or nature legislation that requires environmental monitoring and retrospective ERA. This limitation is due mainly to the availability of baselines, which define acceptable versus unacceptable environmental effects on the key attributes of sentinel species, populations and/or communities, such as reproductive status, abundance, or diversity. Nevertheless, very few regulatory case examples exist in which SPGs incorporate effect magnitude, spatial extent, and temporal duration. We conclude that more holistic approaches are needed for defining SPGs, particularly with respect to protecting population sustainability, ecosystem function, and integrity, which are implicit in generic protection goals and explicit in the International Programme for Chemical Safety (IPCS) definition of "adverse effect." A possible solution, which the chemical industry is currently assessing, is wider application of the ecosystem services approach proposed by the European Food Safety Authority (EFSA) for the risk assessment of PPPs. Integr Environ Assess Manag 2017;13:17-37. © 2016 SETAC.

Assessing the health effects of climate change in Alaska with community-based surveillance

The environmental effects of climate change are greatest in the northern latitudes. There is a need for epidemiological investigations to assess the health impacts of climate change on the health of residents of the circumpolar north. This study employed a participatory, community-based surveillance system to collect repeated observations of environmental conditions and syndromic health outcomes in sentinel communities across three ecologically distinct regions of Alaska. The study revealed that unintentional injury was significantly more likely in months when respondents reported unseasonable environmental conditions, and particularly so when they changed travel plans as a consequence of those conditions. The study also found that incidence of respiratory syndromes, such as pollen allergies and asthma, were significantly higher during months when unseasonable environmental conditions were observed. We conclude that unseasonable environmental conditions likely associated with climate change are having adverse effects on the health of circumpolar northern populations.

Evidence of suppression of onchocerciasis transmission in the Venezuelan Amazonian focus.

BackgroundThe World Health Organization (WHO) has set goals for onchocerciasis elimination in Latin America by 2015. Most of the six previously endemic countries are attaining this goal by implementing twice a year (and in some foci, quarterly) mass ivermectin (Mectizan®) distribution. Elimination of transmission has been verified in Colombia, Ecuador and Mexico. Challenges remain in the Amazonian focus straddling Venezuela and Brazil, where the disease affects the hard-to-reach Yanomami indigenous population. We provide evidence of suppression of Onchocerca volvulus transmission by Simulium guianense s.l. in 16 previously hyperendemic Yanomami communities in southern Venezuela after 15 years of 6-monthly and 5 years of 3-monthly mass ivermectin treatment.MethodsBaseline and monitoring and evaluation parasitological, ophthalmological, entomological and serological surveys were conducted in selected sentinel and extra-sentinel communities of the focus throughout the implementation of the programme.ResultsFrom 2010 to 2012–2015, clinico-parasitological surveys indicate a substantial decrease in skin microfilarial prevalence and intensity of infection; accompanied by no evidence (or very low prevalence and intensity) of ocular microfilariae in the examined population. Of a total of 51,341 S. guianense flies tested by PCR none had L3 infection (heads only). Prevalence of infective flies and seasonal transmission potentials in 2012–2013 were, respectively, under 1 % and 20 L3/person/transmission season. Serology in children aged 1–10 years demonstrated that although 26 out of 396 (7 %) individuals still had Ov-16 antibodies, only 4/218 (2 %) seropositives were aged 1–5 years.ConclusionsWe report evidence of recent transmission and morbidity suppression in some communities of the focus representing 75 % of the Yanomami population and 70 % of all known communities. We conclude that onchocerciasis transmission could be feasibly interrupted in the Venezuelan Amazonian focus.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1313-z) contains supplementary material, which is available to authorized users.

Transmission of Onchocerca volvulus by Simulium neavei in Mount Elgon focus of Eastern Uganda has been interrupted.

The study determined that Simulium neavei-transmitted onchocerciasis in Mount Elgon onchocerciasis focus had been interrupted. Annual mass treatment with ivermectin changed to two times per year along with vector elimination in 2007. Then, baseline microfilaria (mf) prevalence data of 1994 in five sentinel communities were compared with follow-up data in 2005 and 2011. Blood spots from 3,051 children obtained in 2009 were analyzed for Onchocerca volvulus immunoglobulin G4 antibodies. Fresh water crab host captures and blackflies collected indicated their infestation with larval stages of S. neavei and presence or absence of the vector, respectively. Mf rates dropped from 62.2% to 0.5%, and 1 (0.03%) of 3,051 children was positive for O. volvulus antibodies. Crab infestation dropped from 41.9% in 2007 to 0%, and S. neavei biting reduced to zero. Both remained zero for the next 3 years, confirming interruption of onchocerciasis transmission, and interventions were halted.

Interruption of Onchocerca volvulus transmission in Northern Venezuela.

BackgroundOnchocerciasis is caused by Onchocerca volvulus and transmitted by Simulium species (black flies). In the Americas, the infection has been previously described in 13 discrete regional foci distributed among six countries (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela) where more than 370,000 people are currently considered at risk. Since 2001, disease control in Venezuela has relied on the mass drug administration to the at-risk communities. This report provides empirical evidence of interruption of Onchocerca volvulus transmission by Simulium metallicum in 510 endemic communities from two Northern foci of Venezuela, after 10–12 years of 6-monthly Mectizan® (ivermectin) treatment to all the eligible residents.MethodsIn-depth entomologic and epidemiologic surveys were serially conducted from 2001–2012 in selected (sentinel and extra-sentinel) communities from the North-central (NC) and North-east (NE) onchocerciasis foci of Venezuela in order to monitor the impact of ivermectin treatment.ResultsFrom 2007–2009, entomological indicators in both foci confirmed that 0 out of 112,637 S. metallicum females examined by PCR contained L3 infection in insect heads. The upper bound of the 95% confidence intervals of the infective rate of the vector reached values below 1% by 2009 (NC) and 2012 (NE). Additionally, after 14 (NC) and 22 (NE) rounds of treatment, the seasonal transmission potential (±UL CIs) of S. metallicum was under the critical threshold of 20 L3 per person per season. Serological analysis in school children < 15 years-old demonstrated that 0 out of 6,590 individuals were harboring antibodies to Ov-16. Finally, epidemiological surveys made during 2010 (NC) and 2012 (NE) showed no evidence of microfilariae in the skin and eyes of the population.ConclusionsThese results meet the WHO criteria for absence of parasite transmission and disease morbidity in these endemic areas which represent 91% of the population previously at-risk in the country. Consequently, the two Northern foci are currently under post-treatment onchocerciasis surveillance status in Venezuela.

Interruption of Transmission of Onchocerca volvulus in the Southern Chiapas Focus, México

BackgroundThe Southern Chiapas focus of onchocerciasis in Southern Mexico represents one of the major onchocerciasis foci in Latin America. All 559 endemic communities of this focus have undergone semi-annual mass treatment with ivermectin since 1998. In 50 communities of this focus, ivermectin frequency shifted from twice to four times a year in 2003; an additional 113 communities were added to the quarterly treatment regimen in 2009 to achieve a rapid suppression of transmission.Methodology/Principal findingsIn-depth epidemiologic and entomologic assessments were performed in six sentinel communities (which had undergone 2 rounds of ivermectin treatment per year) and three extra-sentinel communities (which had undergone 4 rounds of ivermectin treatment per year). None of the 67,924 Simulium ochraceum s.l. collected from this focus during the dry season of 2011 were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in an upper bound of the 95% confidence interval (95%-ULCI) of the infective rate in the vectors of 0.06/2,000 flies examined. Serological assays testing for Onchocerca volvulus exposure conducted on 4,230 children 5 years of age and under (of a total population of 10,280 in this age group) revealed that 2/4,230 individuals were exposed to O. volvulus (0.05%; one sided 95% confidence interval = 0.08%).Conclusions/SignificanceThe in-depth epidemiological and entomological findings from the Southern Chiapas focus meet the criteria for interruption of transmission developed by the international community.

Urine heme dipsticks are useful in monitoring the impact of Praziquantel treatment on Schistosoma haematobium in sentinel communities of Delta State, Nigeria

Nigeria is highly endemic for infection with Schistosoma haematobium, which most commonly manifests itself with blood in urine. To monitor the impact of annual mass drug administration (MDA) with Praziquantel for S. haematobium in Delta State, Nigeria, cross-sectional hematuria surveys of school children were conducted in 8 sentinel villages (SVs) at baseline (n=240) and after two annual doses (n=402). We assessed the comparability of three assessments of hematuria (child's reported history, nurse visual diagnosis (NVD) and dipstick) to determine the need for mass treatment. Dipstick was considered to be the gold standard. Prior to treatment, history and NVD each identified only the 3 most highly prevalent SVs, and overall this represented just 37.5% of the 8 SVs in need of treatment. Following treatment, after dipstick prevalence decreased by 88.5% (p<0.001), and history and NVD identified only one of two villages still needing treatment. The study suggests that dipsticks should be the recommended method for launching and monitoring mass treatment for S. haematobium.

Lack of active Onchocerca volvulus transmission in the northern Chiapas focus of Mexico.

The northern Chiapas onchocerciasis focus has undergone 11 years of ivermectin mass treatment. No evidence of microfilariae in the cornea and/or anterior chamber of the eye or in skin snips was seen in residents examined in 2006 in two sentinel communities (upper limit of the 95% confidence interval [UL 95% CI] = 0.5% and 0.3%, respectively). In children 10 and under, 0 of 305 were found to harbor antibodies to Ov16, a marker of parasite exposure; 0 of 4,400 Simulium ochraceum s.l. collected in 2005 contained parasite DNA, giving an UL 95% CI for the infective rate of 0.9/2,000, and an UL 95% CI of the seasonal transmission potential of 1.2 L3/person. These data, assumed to be representative of the focus as a whole, suggest that there is no ongoing transmission of Onchocerca volvulus in the northern Chiapas focus. Community-wide treatments with ivermectin were halted in 2008, and a post-treatment surveillance phase was initiated.

Interruption of Transmission of Onchocerca volvulus in the Oaxaca Focus, Mexico

All endemic communities of the Oaxaca focus of onchocerciasis in southern Mexico have been treated annually or semi-annually with ivermectin since 1994. In-depth epidemiologic assessments were performed in communities during 2007 and 2008. None of the 52,632 Simulium ochraceum s.l. collected in four sentinel communities was found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in an upper bound of the infection rate in the vectors of 0.07/2,000. The prevalence of microfilariae (mf) in the cornea and/or anterior chamber of the eye was also zero (0 of 1,039 residents examined; 95%-UL = 0.35%). Similarly, all 1,164 individuals examined by skin biopsy were mf negative (95%-UL = 0.31%), and sera collected from 3,569 children from 25 communities did not harbor Ov16 IgG4-antibodies (95%-UL = 0.09%). These meet the criteria for absence of morbidity and parasite transmission in the Oaxaca focus. As a result mass treatments with ivermectin were halted in 2009.

After a decade of annual dose mass ivermectin treatment in Cameroon and Uganda, onchocerciasis transmission continues

To evaluate the effectiveness of 10 years' annual single dose ivermectin treatment on onchocerciasis transmission in hyperendemic areas of Cameroon and Uganda. Baseline nodule and microfilaria ('skin snip') prevalence data were available from 10 hyperendemic sentinel communities in Cameroon (from 1996) and hyperendemic 20 sentinel communities in Uganda (from 1993). We returned to these villages in 2005, 10 months after the last annual ivermectin distribution, to repeat the cross-sectional surveys. Each sentinel community reported a mean interval treatment coverage of eligible persons of >88% (range 37-100%). Data were analyzed for more than 6200 person examinations. In Cameroon, 719 people >or=10 years were examined at the baseline survey in 1996 and 838 at the follow-up survey in 2005. In Uganda, 1590 people >or=10 years were examined at the baseline survey in 1993 and 2122 people at the follow-up survey in 2005. We also examined children under 10 in Cameroon (1996, n = 185; 2005, n = 448) and Uganda (1993, n = 177; 2005, n = 130). In Uganda, the vitality of worms was judged using standard histological criteria in 80 nodules excised in 2005. The prevalence of microfilaria carriers among older children and adults (>or=10 years) in Cameroon sentinel communities dropped from 70.1% to 7.04% (P < 0.0001) over the 10-year treatment period; that of nodule carriers from 58% to 9.55% (P < 0.0001). Similarly, in Uganda, the prevalence of microfilaria carriers fell from 71.9% to 7.49% (P < 0.0001) over the 13-year treatment period, and that of nodule carriers from 53.21% to 9.66% (P < 0.0001). The number of microfilaria carriers among children <10 years in Cameroon decreased from 29.73% to 3.8% (P < 0.0001), and in Uganda from 33.89% to 3.1% (P < 0.0001). In 2005, worms excised from nodules in Uganda, 81.4% of males remained alive, and 64% of females, with 24% of them inseminated. A decade or more of annual single dose ivermectin treatment in hyperendemic areas has reduced onchocerciasis to 'hypoendemicity', but onchocerciasis transmission persists. For now, annual treatment with ivermectin should be continued in formerly mesoendemic and hyperendemic zones.

Could Neurocysticercosis Be the Cause of “Onchocerciasis-Associated” Epileptic Seizures?

We conducted a nodule prevalence survey in four onchocerciasis sentinel communities in Moyo and two in Kanungu districts of Uganda. Seven (33.3%) out of 21 excised "onchocercomas" (nodules) in Moyo District and excised onchocercomas from four of six persons in Kanungu District turned out to be cysts of Taenia solium. We concluded that the prediction of nodule prevalence for noninvasive rapid epidemiologic assessment (REA) to target areas for mass chemotherapy with ivermectin in the African Program for Onchocerciasis Control (APOC) supported areas may have been influenced by other pathologies. T. solium infection may be the main cause of "onchocerciasis-associated epileptic seizures" in many onchocerciasis endemic communities that have been causally linked to onchocerciasis. Lastly, widespread neurocysticercosis may be a concern in mass treatment programs that provide praziquantel (for managing schistosomiasis) or albendazole (for managing intestinal worms or lymphatic filariasis) because these drugs may kill cerebral cysticerci, resulting in severe adverse events.

Evidence for Suppression of Onchocerca volvulus Transmission in the Oaxaca Focus in Mexico

Entomologic and serologic surveys were performed in four sentinel communities in the Oaxaca focus in southern Mexico to assess the level of transmission and exposure incidence to Onchocerca volvulus. All communities have been receiving ivermectin mass treatment twice per year since 1997. In one community, parasite DNA was detected by polymerase chain reaction-enzyme-linked immunosorbent assay in 2004 in one pool of 50 vector heads of 170 such pools (8,500 flies) examined, which indicated an estimated transmission potential of 6.7 third-stage larvae/person/year. No evidence for transmission was found in the three other communities in 13,650 flies examined. All persons in a cohort consisting of 117 children in the four communities remained serologically negative for antibodies recognizing a cocktail of recombinant antigens over a four-year period from 2001 to 2004, which indicated an exposure incidence of 0%. Taken together, these data suggest that transmission has been suppressed in the four communities.

Impact of long-term treatment of onchocerciasis with ivermectin in Ecuador: potential for elimination of infection

BackgroundOnchocerciasis is a leading cause of blindness worldwide, hence elimination of the infection is an important health priority. Community-based treatment programs with ivermectin form the basis of control programs for the disease in Latin America. The long-term administration of ivermectin could eliminate Onchocerca volvulus infection from endemic areas in Latin America.MethodsA strategy of annual to twice-annual treatments with ivermectin has been used for onchocerciasis in endemic communities in Ecuador for up to 14 years. The impact of ivermectin treatment on ocular morbidity, and O. volvulus infection and transmission was monitored in seven sentinel communities.ResultsOver the period 1990–2003, high rates of treatment coverage of the eligible population were maintained in endemic communities (mean 85.2% per treatment round). Ivermectin reduced the prevalence of anterior segment disease of the eye to 0% in sentinel communities and had a major impact on the prevalence and transmission of infection, with possible elimination of infection in some foci.ConclusionThe distribution of ivermectin in endemic communities in Ecuador might have eliminated ocular morbidity and significant progress has been made towards elimination of the infection. A strategy of more frequent treatments with ivermectin may be required in communities where the infection persists to achieve the objective of elimination of the infection from Ecuador. The elimination of the infection from an endemic country in Latin America would be a major public health achievement and could stimulate the implementation of elimination strategies in other endemic countries.

COMMUNITY-WIDE REDUCTION IN PREVALENCE AND INTENSITY OF INTESTINAL HELMINTHS AS A COLLATERAL BENEFIT OF LYMPHATIC FILARIASIS ELIMINATION PROGRAMS

Annual mass treatment with antifilarial drugs is the cornerstone of the global program to eliminate lymphatic filariasis (LF). Although the primary goal of the program is to interrupt transmission of LF, additional public health benefits also are expected because of the known anthelminthic properties of these drugs. Since rapid re-infection with intestinal helminths occurs following treatment, annual de-worming may not be sufficient to produce a lasting reduction in the prevalence and intensity of these infections. We conducted stool examinations in four sentinel communities before and approximately nine months after each of two rounds of mass drug administration (MDA) with diethylcarbamazine and albendazole in the context of an LF elimination program in Leogane, Haiti. At baseline, overall Ascaris, Trichuris, and hookworm infection prevalences were 20.9%, 34.0%, and 11.2%, respectively (n = 2,716 stools). Nine months after the second MDA, Ascaris, Trichuris and hookworm prevalences had decreased significantly, to 14.1%, 14.6%, and 2.0%, respectively (n = 814 stools). Infection intensity decreased significantly for all three parasites as well. These results demonstrate that substantial reductions in intestinal helminth infections are associated with mass treatment of filariasis in Haiti and are consistent with the conclusion that high levels of coverage for the LF program can decrease transmission of geohelminths.

PCR and Mosquito dissection as tools to monitor filarial infection levels following mass treatment

BackgroundEntomological methods may provide important tools for monitoring the progress of lymphatic filariasis elimination programs. In this study, we compared dissection of the vector, Culex quinquefasciatus, with the polymerase chain reaction (PCR) to assess filarial infection levels in mosquitoes in the context of a lymphatic filariasis elimination program in Leogane, Haiti.MethodsMosquitoes were collected using gravid traps located in 4 sentinel communities with Wuchereria bancrofti microfilaria prevalence that ranged from 0.8% to 15.9%. Captured mosquitoes were divided between dissection, to enumerate W. bancrofti larvae (L1, L2, L3) and desiccation for later analysis by PCR. PCR was conducted on DNA extracts from pooled mosquitoes (1–15 pooled females) utilizing a competitive PCR system with primers specific for the Ssp I repeat. PCR products were analyzed with a hybridization ELISA using probes specific for a control sequence and the Ssp I repeat.ResultsThe prevalence of mosquito infection with W. bancrofti ranged from 0%–3.66% by dissection (L1–L3) and point estimates of infection prevalence, as assayed by PCR, ranged from 0.25% – 9.16%. Following mass treatment, W. bancrofti infection prevalence dropped significantly as determined by PCR and dissection in 2 of the 4 sentinel sites (Leogane and Barrier Jeudi, P = 0.04 and P = 0.005, respectively). Although transmission declined in the other two sites, larval recoveries were low and these changes were not statistically significant.DiscussionOur results suggest that a single round of mass treatment can have an impact on transmission of lymphatic filariasis. The use of entomologic methods as a tool to monitor filariasis programs and the statistical limitations of mosquito trapping are discussed.

Human onchocerciasis in the Amazonian area of southern Venezuela: spatial and temporal variations in biting and parity rates of black fly (Diptera: Simuliidae) vectors.

We investigated some entomological factors underlying altitudinal prevalence variation in the Venezuelan Amazonia human onchocerciasis focus. Spatial and temporal variation in relative abundance, daily biting rate, proportion of parous flies, and monthly parous biting rate were studied for the three main simuliid vectors (based on their vectorial competence: Simulium oyapockense s.l. Floch & Abonnenc approximately = S. incrustatum Lutz << S. guianense s.l. Wise). Yanomami villages were selected among sentinel communities of the ivermectin control program, representing hypo- to hyperendemicity conditions of infection. Spatial variation was explored via increasing village altitude on two river systems (A: Ocamo-Putaco and B: Orinoco-Orinoquito). Temporal variation was studied between 1995 and 1999 by sampling the biting population during dry and rainy mouths. Environmental variables included monthly rainfall and maximum river height. Simuliid species composition itself varied along the altitudinal and prevalence gradient. S. oyapockense s.l. prevailed below 150 m. Above this altitude and up to 240 m, S. incrustatum and S. guianense s.l. became more frequently and evenly collected along A but not along B, where S. incrustatum remained absent. The daily biting rate of S. oyapockense s.l. was higher during the dry season along A, whereas the converse took place along B. Daily biting rate of S. incrustatum was lowest during early rains. By contrast, the daily biting rate of S. guianense s.l. was highest during this period. There was a significant negative cross-correlation between proportion of parous of S. oyapockense s.l. and river height (2 and 3 mo lagged), whereas this variable (1 and 2 mo lagged) was positively correlated with the proportion of parous flies for S. incrustatum. Monthly parous biting rate values suggest that the months contributing most to onchocerciasis transmission in the area are likely to be the dry season and the transition periods between seasons.

The clinical epidemiology of acute diarrhoeal disease in Egyptian children.

We have used a method of surveillance for diarrhea that examines day-point prevalence in sentinel communities in children under 3 years of age in Egypt. The data have been most helpful in designing aspects of the National Control of Diarrheal Diseases Project. We found diarrhea to be most prevalent and most serious in children under 24 months of age in rural areas and in summer and autumn. Children spend on the average 11% of their year with diarrhea nearly 2/3 of which is watery. Mothers are increasingly using oral rehydration therapy; and they are more likely to seek medical help when signs of dehydration occur. The majority of chilren were given less food during diarrhea and about 1/3 are taken off breast milk for a week or more if diarrhea persists. 4 rural and 1 sub-urban community were surveyed for this study from July 1983 to October 1984. Methods included a census to identify households and members a canvass to identify children who had diarrhea within the past 24 hours and a follow-up survey of all children identified with diarrhea in the canvass stage by interviewing the mother. Monthly day-point prevalences over time were also done in 5 communities. Canvassers were mostly local people. (authors modified)