Towards the elimination of onchocerciasis

Prospects for developing efficient targets for the xenomonitoring and control of Simulium damnosum s.l., the major vectors of onchocerciasis in Africa

Despite the ethical issues concerning the continued use of Human Landing Catches (HLC) to monitor the Simulium damnosum complex for epidemiological monitoring of onchocericasis, few attempts to develop alternatives have been reported. In studies on a wild population of S. damnosum in Burkina Faso, we tested visual targets (different sizes and shapes) and olfactory stimuli (CO₂ , and POCA and BG-lure® odour blends) for their ability to attract and collect host seeking blackflies. At each trap, blackflies were caught with appropriately sized electrocuting grids and results from Latin square design tests were compared. Throughout, HLCs captured more blackflies than the targets. Of the traps tested, small targets (0.0625 and 0.5 m² ) were the most efficient visual lure in terms of the number of S. damnosum captured per unit area 1.7-5× more than larger targets. Overall, results suggested that sticky black targets of horizontal rectangular shape (0.125-0.5 m² ) and baited with a POCA and/or CO₂ mixture could provide a cheap practical field alternative to HLC for onchocerciasis xenomonitoring, subject to confirmation that the design has no inherent bias for certain members of the S. damnosum species complex.

Human filariasis in travelers and migrants: a retrospective 25-year analysis at the Institute of Tropical Medicine, Antwerp, Belgium

BACKGROUND

Information on human filariasis in international travelers is scarce. We describe the epidemiology, clinical presentation and outcome of these infections in a reference travel clinic over the past decades.

METHODS

We reviewed all cases of filariasis diagnosed at the Institute of Tropical Medicine, Antwerp, Belgium, from 1994 to 2018. Diagnosis was obtained by either parasitological methods (confirmed) or strict clinical case definitions (probable). We assessed the characteristics of cases at diagnosis and response to therapy within three to 12 months.

RESULTS

A total of 320 patients (median age: 41 years; 71% males) were diagnosed with 327 filarial infections (Wuchereria bancrofti = 6; Onchocerca volvulus = 33, Loa loa = 150, Mansonella perstans = 130; unspecified species = 8). Diagnosis was confirmed in 213/320 (67%) patients. European long-term travelers accounted for 166 patients (52%) and visitors/migrants from tropical countries for another 110 (34%). Central Africa was the likely region of acquisition for 294 (92%) patients. The number of filariasis cases decreased from 21.5/year in average in the nineties to 6.3/year in the last decade, when loiasis became predominant. Cases reported symptoms in > 80% of all filarial infections but mansonellosis (45/123 single infections; 37%). Lymphatic filariasis and onchocerciasis cases responded well to conventional therapy. However, 30% of patients with loiasis and mansonellosis experienced treatment failure (with diethylcarbamazine and levamisole-mebendazole, respectively).

CONCLUSIONS

The burden and species distribution of filariasis in travelers evolved in the past decades. Most presentations were symptomatic. Case management would benefit from more effective therapies for loiasis and mansonellosis.

Inflammatory and regulatory CCL and CXCL chemokine and cytokine cellular responses in patients with patent Mansonella perstans filariasis

Mansonella perstans (Mp) filariasis is present in large populations in sub-Saharan Africa, and to what extent patent Mp infection modulates the expression of immunity in patients, notably their cellular cytokine and chemokine response profile, remains not well known. We studied the spontaneous and inducible cellular production of chemokines (C-X-C motif) ligand 9 (CXCL9) [monokine induced by interferon (IFN)-γ (MIG)], CXCL-10 [inducible protein (IP)-10], chemokine (C-C motif) ligand 24 (CCL24) (eotaxin-2), CCL22 [macrophage-derived chemokine (MDC)], CCL13 [monocyte chemotactic protein-4 (MCP-4)], CCL18 [pulmonary and activation-regulated chemokine (PARC)], CCL17 [thymus- and activation-regulated chemokine (TARC)] and interleukin (IL)-27 in mansonelliasis patients (Mp-PAT) and mansonelliasis-free controls (CTRL). Freshly isolated peripheral mononuclear blood cells (PBMC) were stimulated with helminth, protozoan and bacterial antigens and mitogen [phytohaemagglutinin (PHA)]. PBMC from Mp-PAT produced spontaneously (without antigen stimulation) significantly higher levels of eotaxin-2, IL-27, IL-8, MCP-4 and MDC than cells from CTRL, while IFN-γ-IP-10 was lower in Mp-PAT. Helminth antigens activated IL-27 and MCP-4 only in CTRL, while Ascaris antigen, Onchocerca antigen, Schistosoma antigen, Entamoeba antigen, Streptococcus antigen, Mycobacteria antigen and PHA stimulated MIG release in CTRL and Mp-PAT. Notably, Entamoeba antigen and PHA strongly depressed (P < 0·0001) eotaxin-2 (CCL24) production in both study groups. Multiple regression analyses disclosed in Mp-PAT and CTRL dissimilar cellular chemokine and cytokine production levels being higher in Mp-PAT for CCL24, IL-27, IL-8, MCP-4, MDC and PARC (for all P < 0·0001), at baseline (P < 0·0001), in response to Entamoeba histolytica strain HM1 antigen (EhAg) (P < 0·0001), Onchocerca volvulus adult worm-derived antigen (OvAg) (P = 0·005), PHA (P < 0·0001) and purified protein derivative (PPD) (P < 0·0001) stimulation. In Mp-PAT with hookworm co-infection, the cellular chemokine production of CXCL10 (IP-10) was diminished. In summary, the chemokine and cytokine responses in Mp-PAT were in general not depressed, PBMC from Mp-PAT produced spontaneously and selectively inducible inflammatory and regulatory chemokines and cytokines at higher levels than CTRL and such diverse and distinctive reactivity supports that patent M. perstans infection will not polarize innate and adaptive cellular immune responsiveness in patients.

Field-Based Evidence of Single and Few Doses of Annual Ivermectin Treatment Efficacy in Eliminating Skin Microfilaria Load after a Decade of Intervention

Background

Impact assessment of community-based ivermectin treatment control of onchocerciasis is required to determine its effectiveness. This study was conducted to evaluate geographic coverage and demographic ivermectin treatment compliance.

Methods

The number of village dosage were obtained from the community based distributors. Bioclinical data of participants comprising gender, age, number of treatment received from inception and dosage were obtained. Each participant was subjected to physical examination for palpable nodule and other skin clinical signs and symptoms of onchocerciasis. Visual acuity test was done using the Snellen illiterate E-chart. Eye examination was performed using touch loop and handheld ophthalmoscope. Skin snips from both iliac crests were incubated overnight at 28–32°C and emerged micrifilaria enumerated under an inverted microscope. The changes in epidemiological indices at post-decade of mass drug administration were compared with baseline data.

Results

Village annual ivermectin treatment doses averaged 62%, ranging between 10–100%. Individual treatment compliance rate was generally low with an average of 4 treatments and a range between 0–10. Despite variations in treatment compliance, there were significant improvements in some onchocercal morbidities. These include reduced number and severity of itching, visual impairment, papular onchodermatitis, onchocercomata (palpable nodules) and leopard skin. Ivermectin treatment halted development of new blind cases, except the case of a man who had optic nerve disease and became blind 2 years after ivermectin treatment had commenced. There was a significant overall reduction in parasite burden with very low mean skin microfilaria load of 1.7mf per skin snip and 3.7% skin mf prevalence, compared to baseline data of 17.7mf and 37.9% respectively. The palpable nodule was also drastically reduced from 14.5% to 6.4%. Outcome of this study has practically demonstrated that even a single dose ivermectin treatment is capable of clearing skin mf load on a long-term basis. This assertion is exemplified by the result obtained from Bomjock village that had taken treatment only at inception, and the prevalence rate was reduced from 70% to about 9.0% at post-decade of intervention.

Conclusion

It can be inferred that high demographic coverage with annual treatment doses, it is feasible to attain a shorter time (within a decade) contrary to the anticipated longer-term projection.

Onchocerca volvulus infection and serological prevalence, ocular onchocerciasis and parasite transmission in northern and central Togo after decades of Simulium damnosum s.l. vector control and mass drug administration of ivermectin

Background

Mass drug administration (MDA) of ivermectin has become the main intervention to control onchocerciasis or “river blindness”. In Togo, after many years of MDA, Onchocerca volvulus infection has declined dramatically, and elimination appears achievable, but in certain river basins the current situation remains unknown. We have conducted parasitological, serological, ophthalmological, and entomological assessments in northern and central Togo within the river basins of Ôti, Kéran and Mô.

Methodology/Principal findings

Examinations were completed in 1,455 participants from 11 onchocerciasis sentinel villages, and O. volvulus transmission by Simulium damnosum sensu lato (s.l.) was evaluated. In children (aged 1–10 years), the prevalence of microfilariae (Mf) was 2.3% and in adults it ranged from 5.1 to 13.3%. Positive IgG4 responses to O. volvulus adult (crude) worm antigen (OvAg) and the recombinant Ov16 antigen were in all-ages 48.7% and 34.4%, and 29.1% and 14.9% in children, respectively. In the river basin villages of Kéran, Mô and Ôti, the IgG4 seroprevalences to OvAg in children were 51.7%, 23.5% and 12.7%, respectively, and to the Ov16 antigen 33.3% (Kéran) and 5.2% (Ôti). Onchocerciasis ocular lesions (punctate keratitis, evolving iridocyclitis and chorioretinitis) were observed in children and young adults. O. volvulus-specific DNA (Ov150) was detected by poolscreen in vector samples collected from Tchitchira/Kéran(22.8%), Bouzalo/Mô(11.3%), Baghan/Mô(2.9%) and Pancerys/Ôti(4.9%); prevalences of O. volvulus infection in S. damnosum s.l. were, respectively, 1%, 0.5%, 0.1% and 0.2%.

Conclusions/Significance

In the northern and central river basins in Togo, interruption of O. volvulus transmission has not yet been attained. Patent O. volvulus infections, positive antibody responses, progressive ocular onchocerciasis were diagnosed, and parasite transmission by S. damnosum s.l. occurred close to the survey locations. Future interventions may require approaches selectively targeted to non-complying endemic populations, to the seasonality of parasite transmission and national onchocerciasis control programs should harmonize cross-border MDA as a coordinated intervention.

Mass drug administration (MDA) with ivermectin has become the main tool in the efforts to control and eliminate onchocerciasis (“river blindness”). In some areas, and after many years of MDA, levels of Onchocerca volvulus infection (the causative parasite) have declined greatly, and elimination appears achievable. In certain river basins of northern and central Togo, the present epidemiological situation remains unknown. The guidelines of the World Health Organization recommend that before ivermectin MDA can be stopped, interruption of O. volvulus transmission must be demonstrated. To this end, parasitological, serological, ophthalmological, and entomological assessments were conducted in the Ôti, Kéran and Mô river basins. O. volvulus infections and positive antibody responses were found in children aged ≤10 years and adults. Progressive ocular onchocerciasis was diagnosed, and parasite transmission by Simulium damnosum s.l. (the disease vector) occurred close to the survey locations. Thus, O. volvulus transmission continues in northern and central Togo, and future interventions may require approaches selectively adapted to seasonal migration of non-complying endemic populations in and out of the river basins, as well as seasonal transmission by the vectors. National control programmes should harmonize cross-border MDA as a coordinated intervention.

Recrudescence of onchocerciasis in the Comoé valley in Southwest Burkina Faso

Onchocerciasis control by vector control was instigated in southwest Burkina Faso in January 1969 by ORSTOM/OCCGE, and continued until operations were taken over by the WHO Onchocerciasis Control Programme (OCP) in February 1975, which itself ceased operations in the area in 1989 when onchocerciasis was judged to have been reduced to insignificant levels. Initially (1969-1975) vector immigration maintained unacceptably high levels of transmission, but OCP was much larger than the preceding campaign and in 1975 the Annual Transmission Potential (ATP) dropped below 100 at all sites in the Comoé river valley except Folonzo, which continued to be subject to reinvasion, along with the whole of the Léraba river valley. However, after the southern extension of the OCP in 1979, ATPs dropped below 100 everywhere in the Comoé basin (including the Léraba valley), and further dropped to insignificant levels after the western extension of the OCP in 1985. Thus transmission dropped more quickly in the Comoé river valley than the Léraba river valley (which had been subject to vector reinvasion), and this was also reflected in prevalence of microfilaraemia in the human population. After 1986 prevalence was less than 5% in all villages in the Comoé river valley (except for two, which subsequently dropped to 0% and 3.7% by 1999). However, in 2001 (12 years after the cessation of vector control) the prevalence in one village in the Comoé river valley had increased to 39.6%, and two more had increased above 5% by 2007. New epidemiological surveys in 2011 and 2012 showed that in 13 out of 30 villages in the Comoé river valley prevalence of microfilaraemia was above 5%, although this was not observed in the Léraba river valley where prevalence remained low. This is the first documented case of recrudescence of onchocerciasis in the old OCP area, and the reasons are not clear. It is possible that there has been immigration of parasites with humans or vectors from areas where there has been a shorter period of control, or that control has been less effective. It is possible that in spite of very low levels of transmission the local parasite population was never reduced to a level below the transmission breakpoint, or that there has been a local recrudescence due to stochastic population effects. In any case it is clear that the distribution of ivermectin against lymphatic filariasis in the area since 2004 has failed to prevent the recrudescence of onchocerciasis, and the Burkina Faso Programme National de Lutte contre l'Onchocercose (PNLO - Ministere de la Santé) has instigated a programme of Community Directed Treatment with Ivermectin specifically aimed at onchocerciasis in accordance with the strategy developed by APOC and recommended to governments by OCP when it was dissolved in 2002.

Monitoring rare serious adverse events from a new treatment and testing for a difference from historical controls

Background We detail the design of a study to monitor the safety of including albendazole to an existing treatment regimen to eliminate lymphatic filariasis. We wish to show that this new regimen does not increase the rate of a rare serious adverse event (SAE) compared to the old regimen. Controlled but small clinical trials have not detected any increase in the SAE using albendazole, and it is known to have added benefits; therefore, it is unethical to randomize patients to the old regimen.

Purpose A sample size for the new regimen is needed to test that the new rate of SAE is noninferior to the historic rate. If the new regimen does have an inferior rate of SAE then we wish to stop the study early. This setup is different from traditional early stopping for efficacy and futility. In that traditional case, the two stopping decisions are relative to the same null hypothesis of equality, while in our setup, we have two different null hypotheses: the noninferiority null and the equality null. When testing the former, we need not stop early if the new regimen appears better because no subjects are receiving the old regimen anymore anyway. When testing the equality of SAE rates, however, we want to stop early if the new regimen has a significantly higher rate of SAE.

Methods We create a design that uses an exact difference in proportions test for testing noninferiority, but calculates maximal sample size based on conditional power which treats the historical rates as true rates. The design allows for early stopping if the new treatment appears inferior with respect to SAE rate but makes no corrections for multiple testing. We explore the properties of this naive design without assuming the historical rates are known.

Results For our example, we show that our naive design strategy bounds the type I error of the noninferiority hypothesis in all cases and bounds it for the equality hypothesis at 0.05, as long as the true SAE rate is <0.00015. The same design has unconditional power for the noninferiority hypothesis greater than the nominal 80% as long as the true SAE rate for both regimens are <0.00025.

Limitations The type I and power results above hold only for our historical sample size of 17 877. We expect similar type I and power properties to hold with studies with SAE rates similar or less (i.e., < 0.00015) and historical sample sizes similar or smaller.

Conclusions Our design for comparing very rare historical SAE rates to SAE rates of a new treatment has large power to conclude noninferiority of the new treatment SAE rate when both rates are equal, but allows early stopping if the new SAE rates are worse. Clinical Trials 2007; 4: 598—610. http://ctj.sagepub.com

Ivermectin: A Reflection on Simplicity (Nobel Lecture)

Parasitic diseases including river blindness and lymphatic filariasis affect hundreds of millions of people annually. The discovery of the drug ivermectin has provided humankind with a powerful new means to combat these severe diseases. To a very large extent the drug was brought about by "simple" science.

Immunotherapy with mutated onchocystatin fails to enhance the efficacy of a sub-lethal oxytetracycline regimen against Onchocerca ochengi

Human onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus, has been successfully controlled by a single drug, ivermectin, for over 25 years. Ivermectin prevents the disease symptoms of severe itching and visual impairment by killing the microfilarial stage, but does not eliminate the adult parasites, necessitating repeated annual treatments. Mass drug administration with ivermectin does not always break transmission in forest zones and is contraindicated in individuals heavily co-infected with Loa loa, while reports of reduced drug efficacy in Ghana and Cameroon may signal the development of resistance. An alternative treatment for onchocerciasis involves targeting the essential Wolbachia symbiont with tetracycline or its derivatives, which are adulticidal. However, implementation of antibiotic therapy has not occurred on a wide scale due to the prolonged treatment regimen required (several weeks). In the bovine Onchocerca ochengi system, it has been shown previously that prolonged oxytetracycline therapy increases eosinophil counts in intradermal nodules, which kill the adult worms by degranulating on their surface. Here, in an "immunochemotherapeutic" approach, we sought to enhance the efficacy of a short, sub-lethal antibiotic regimen against O. ochengi by prior immunotherapy targeting onchocystatin, an immunomodulatory protein located in the adult female worm cuticle. A key asparagine residue in onchocystatin was mutated to ablate immunomodulatory activity, which has been demonstrated previously to markedly improve the protective efficacy of this vaccine candidate when used as an immunoprophylactic. The immunochemotherapeutic regimen was compared with sub-lethal oxytetracycline therapy alone; onchocystatin immunotherapy alone; a gold-standard prolonged, intermittent oxytetracycline regimen; and no treatment (negative control) in naturally infected Cameroonian cattle. Readouts were collected over one year and comprised adult worm viability, dermal microfilarial density, anti-onchocystatin IgG in sera, and eosinophil counts in nodules. Only the gold-standard antibiotic regimen achieved significant killing of adult worms, a profound reduction in microfilarial load, and a sustained increase in local tissue eosinophilia. A small but statistically significant elevation in anti-onchocystatin IgG was observed for several weeks after immunisation in the immunotherapy-only group, but the antibody response in the immunochemotherapy group was more variable. At 12 weeks post-treatment, only a transient and non-significant increase in eosinophil counts was apparent in the immunochemotherapy group. We conclude that the addition of onchocystatin immunotherapy to a sub-lethal antibiotic regimen is insufficient to induce adulticidal activity, although with booster immunisations or the targeting of additional filarial immunomodulatory proteins, the efficacy of this strategy could be strengthened.

Late-onset onchocercal skin disease among Ethiopian immigrants

BACKGROUND

Onchocerciasis is an infectious disease caused by the filaria Onchocerca volvulus. Very little is known regarding onchocerciasis imported from endemic to nonendemic areas.

OBJECTIVES

To evaluate pruritic dermatitis simulating atopic dermatitis in Ethiopian immigrants in Israel.

PATIENTS AND METHODS

A retrospective study of 27 Ethiopian immigrants to Israel was conducted. Demographics and clinical and laboratory data were collected.

RESULTS

Of the group of 27 patients, 10 (37%) were men and 17 (63%) were women. The average age at referral was 29 years. All of the patients emigrated from Kuwara, Ethiopia. Diagnosis was done by either positive skin snip test or immunoglobulin (Ig) G4 serology of onchocerciasis in 14 patients. The most common presentation was a combination of lichenified onchodermatitis with atrophy and depigmentation (36%). Eosinophilia and elevated IgE levels were common. Seventeen patients were treated with a single administration of oral ivermectin 200 μg mg(-1). Thirteen patients responded to the treatment.

CONCLUSIONS

Immigrants from endemic regions to developed countries presenting with pruritic diseases, especially those with a clinical picture suggestive of atopic dermatitis, should be evaluated for possible onchocerciasis infection. Ivermectin, a relatively safe and low-cost treatment, should be considered even in the absence of a proven disease. Physicians should have a high index of suspicion in patients with the corresponding residential history.

Knowledge and beliefs about onchocerciasis among rural inhabitants in an endemic area of Ethiopia

A cross-sectional study was conducted to assess the knowledge and beliefs about causes, transmission, prevention and control of onchocerciasis among rural inhabitants in an endemic area of Ethiopia. Descriptive and quantitative information was collected using focus group discussions and a pretested structured questionnaire. Onchocerciasis affected and unaffected respondents' knowledge and beliefs regarding onchocerciasis were compared. Overall, 75.9% (192/253) of study subjects were aware about onchocerciasis. During the survey, 66.9% of affected, and 45.5% of unaffected respondents knew that onchocerciasis was transmitted through blackfly bites. About 53% of unaffected and 60% of affected respondents thought that onchocerciasis was preventable and the majority of the affected respondents felt that it was curable. Chi-square statistical analysis found a significant association between affected and unaffected individual's knowledge and beliefs about causes, transmission, prevention and control of onchocerciasis. Although the majority of respondents had ample awareness, a sizable proportion still had misconceptions and misunderstandings about causes, transmission, prevention and control of onchocerciasis. Therefore, appropriate communication strategies should be developed to create the awareness regarding the role of blackflies in onchocerciasis transmission, the importance of proper prevention techniques, early diagnosis and treatment to bring a constructive outcome in the near future.

Single nucleotide polymorphisms in β-tubulin selected in Onchocerca volvulus following repeated ivermectin treatment: possible indication of resistance selection

The control of onchocerciasis or river blindness by mass treatment of the population with ivermectin (IVM) has been a great success until now, so that in certain foci its elimination has become feasible. However, after more than 20 years of repeated IVM mass treatment, the disease still persists in many endemic countries. Sub-optimal responses and genetic changes have been reported in Onchocerca volvulus populations under high IVM pressure but more work is needed to determine whether resistance is developing. The situation needs to be urgently clarified to preserve the achievements of onchocerciasis control programs. In this study, O. volvulus adult worms were collected from the same individuals, before IVM exposure and following three years of annual or three-monthly treatments at 150 μg/kg or 800 μg/kg. Four single nucleotide polymorphisms (SNPs) occurring in the β-tubulin gene of these parasites were investigated. We found changes in genotype frequencies in O. volvulus β-tubulin gene associated with IVM treatments. The SNP at position 1545 (A/G) showed a significant increase in frequency of the less common nucleotide in the female worms following treatment. After 13 three-monthly treatments, female worm homozygotes with the less common genotype, prior to treatment, increased in frequency. The selected homozygotes, as well as heterozygotes, appeared to be less fertile (without or with very few embryonic stages in their uteri) than the wild-type homozygotes. These results provide additional evidence for genetic selection and strengthen the warning that selection for IVM resistance may be occurring in some O. volvulus populations.

Impact of long-term treatment of onchocerciasis with ivermectin in Kaduna State, Nigeria: first evidence of the potential for elimination in the operational area of the African Programme for Onchocerciasis Control

Background

Onchocerciasis can be effectively controlled as a public health problem by annual mass drug administration of ivermectin, but it was not known if ivermectin treatment in the long term would be able to achieve elimination of onchocerciasis infection and interruption of transmission in endemic areas in Africa. A recent study in Mali and Senegal has provided the first evidence of elimination after 15-17 years of treatment. Following this finding, the African Programme for Onchocerciasis Control (APOC) has started a systematic evaluation of the long-term impact of ivermectin treatment projects and the feasibility of elimination in APOC supported countries. This paper reports the first results for two onchocerciasis foci in Kaduna, Nigeria.

Methods

In 2008, an epidemiological evaluation using skin snip parasitological diagnostic method was carried out in two onchocerciasis foci, in Birnin Gwari Local Government Area (LGA), and in the Kauru and Lere LGAs of Kaduna State, Nigeria. The survey was undertaken in 26 villages and examined 3,703 people above the age of one year. The result was compared with the baseline survey undertaken in 1987.

Results

The communities had received 15 to 17 years of ivermectin treatment with more than 75% reported coverage. For each surveyed community, comparable baseline data were available. Before treatment, the community prevalence of O. volvulus microfilaria in the skin ranged from 23.1% to 84.9%, with a median prevalence of 52.0%. After 15 to 17 years of treatment, the prevalence had fallen to 0% in all communities and all 3,703 examined individuals were skin snip negative.

Conclusions

The results of the surveys confirm the finding in Senegal and Mali that ivermectin treatment alone can eliminate onchocerciasis infection and probably disease transmission in endemic foci in Africa. It is the first of such evidence for the APOC operational area.

Global health: neglected diseases and access to medicines

The World Health Organization has developed a comprehensive plan to deal with neglected tropical diseases (NTDs). Compared with a decade ago, more resources are being spent to address the problem of neglected diseases, and considerable progress has been made. However, NTDs remain neglected, deepening the global inequities in health. The current efforts do not implement a multiprong strategy and are effective in the short term, but do not generate long-term, sustainable solutions. This article discusses the current successes in providing access to medicine for treatment of a multitude of neglected diseases, and the opportunities to achieve global equality in health.

Onchocerciasis in the Americas: from arrival to (near) elimination

Onchocerciasis (river blindness) is a blinding parasitic disease that threatens the health of approximately 120 million people worldwide. While 99% of the population at-risk for infection from onchocerciasis live in Africa, some 500,000 people in the Americas are also threatened by infection. A relatively recent arrival to the western hemisphere, onchocerciasis was brought to the New World through the slave trade and spread through migration. The centuries since its arrival have seen advances in diagnosing, mapping and treating the disease. Once endemic to six countries in the Americas (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela), onchocerciasis is on track for interruption of transmission in the Americas by 2012, in line with Pan American Health Organization resolution CD48.R12. The success of this public health program is due to a robust public-private partnership involving national governments, local communities, donor organizations, intergovernmental bodies, academic institutions, non-profit organizations and the pharmaceutical industry. The lessons learned through the efforts in the Americas are in turn informing the program to control and eliminate onchocerciasis in Africa. However, continued support and investment are needed for program implementation and post-treatment surveillance to protect the gains to-date and ensure complete elimination is achieved and treatment can be safely stopped within all 13 regional foci.

Control of onchocerciasis in Africa: threshold shifts, breakpoints and rules for elimination

Control of onchocerciasis in Africa is currently based on annual community-directed treatment with ivermectin (CDTI) which has been assumed to be not efficient enough to bring about elimination. However, elimination has recently been reported to have been achieved by CDTI alone in villages of Senegal and Mali, reviving debate on the eradicability of onchocerciasis in Africa. We investigate the eradicability of onchocerciasis by examining threshold shifts and breakpoints predicted by a stochastic transmission model that has been fitted extensively to data. We show that elimination based on CDTI relies on shifting the threshold biting rate to a level that is higher than the annual biting rate. Breakpoints become relevant in the context of when to stop CDTI. In order for the model to predict a good chance for CDTI to eliminate onchocerciasis, facilitating factors such as the macrofilaricidal effect of ivermectin must be assumed. A chart predicting the minimum efficacy of CDTI required for elimination, dependent on the annual biting rate, is provided. Generalisable recommendations into strategies for the elimination of onchocerciasis are derived, particularly referring to the roles of vectors, the residual infection rate under control, and a low-spreader problem originating from patients with low parasite burdens.

Prevalence and risk factors for near and far visual difficulty in Burkina Faso

PURPOSE

To determine the prevalence and risk factors for near and far visual difficulty in Burkina Faso.

METHODS

Population-based data were used from the World Health Survey done in Burkina Faso in 2002-2003;2003 (n=4,822 adults). Near and far visual difficulty were assessed by questions about difficulty seeing and recognizing an object at arm's length and about difficulty seeing and recognizing a person across the road. Prevalence estimates were adjusted for the multi-stage, stratified, random cluster sampling design. Logistic regression was used to identify independent risk factors.

RESULTS

The overall prevalence of any near and far visual difficulty was 10% (standard error [SE] = 0.7%) and 13% (SE=0.9%) respectively. Prevalence estimates were strongly associated with age with 48% (SE=4.2%) and 66% (SE=3.9%) of those >or= 65 years old having near or far visual difficulty (P < 0.001). Only 5% (SE=0.6%) of people wore glasses. We identified two potentially modifiable variables associated with near visual difficulty: a cooking stove in the same room as sleeping area (Odds Ratio [OR]=1.45, 95% Confidence Interval [CI] 1.01, 2.02) and high fruit consumption (OR=0.65, 95% CI 0.50, 0.86).

CONCLUSION

The prevalence of visual difficulty was high in Burkina Faso. Efforts to confirm these findings with cooking stove location and fruit consumption should be undertaken in this population.

Polyparasitism and its impact on the immune system

Parasitic infections are common in many tropical and sub-tropical regions of the world and concomitant infection, polyparasitism, is the rule rather than the exception in such areas. At the immunological level, different parasites induce quite different responses characterised, for example, by protozoa that polarise responses towards Th1, whilst helminths are strong Th2 and regulatory T cell inducers. The question of how the co-existence of such parasites within the same host might influence the immunological responses to each species and, more importantly, whether such interactions affect resistance, susceptibility or clinical outcome, needs to be addressed in well-designed studies of sufficient power. The current paper discusses what we know as well as the gaps in our knowledge of polyparasitism.

Mapping, monitoring, and surveillance of neglected tropical diseases: towards a policy framework

As national programmes respond to the new opportunities presented for scaling up preventive chemotherapy programmes for the coadministration of drugs to target lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis, and trachoma, possible synergies between existing disease-specific policies and protocols need to be examined. In this report we compare present policies for mapping, monitoring, and surveillance for these diseases, drawing attention to both the challenges and opportunities for integration. Although full integration of all elements of mapping, monitoring, and surveillance strategies might not be feasible for the diseases targeted through the preventive chemotherapy approach, there are opportunities for integration, and we present examples of integrated strategies. Finally, if advantage is to be taken of scaled up interventions to address neglected tropical diseases, efforts to develop rapid, inexpensive, and easy-to-use methods, whether disease-specific or integrated, should be increased. We present a framework for development of an integrated monitoring and evaluation system that combines both integrated and disease-specific strategies.

Integration of control of neglected tropical diseases into health-care systems: challenges and opportunities

Although progress has been made in the fight against neglected tropical diseases, current financial resources and global political commitments are insufficient to reach the World Health Assembly's ambitious goals. Increased efforts are needed to expand global coverage. These efforts will involve national and international harmonisation and coordination of the activities of partnerships devoted to control or elimination of these diseases. Rational planning and integration into regular health systems is essential to scale up these interventions to achieve complete eradication of these diseases. Programmes with similar delivery strategies and interventions-such as those for onchocerciasis, lymphatic filariasis, and soil-transmitted helminthiasis-could be managed on the same platform and together. Furthermore, better-resourced programmes-such as those for malaria, HIV/AIDS, and tuberculosis-could work closely with those for neglected tropical diseases to their mutual benefit and the benefit of the entire health system.

Epidemiology and control of onchocerciasis: the threshold biting rate of savannah onchocerciasis in Africa

Control of onchocerciasis currently focuses on community-directed treatment with the microfilaricide ivermectin which effectively kills Onchocerca volvulus microfilariae in the human host. The feasibility of elimination by this control strategy has recently been reported for some foci in Africa which has rekindled discussions on evaluating the threshold conditions of elimination of onchocerciasis. We developed a stochastic model based on a master equation which predicts, based on data from West and Central Africa, that elimination of savannah onchocerciasis can be expected around a threshold biting rate of 730 bites per person per year, ranging region-specifically roughly from 230 to 2300 bites per person and year. The threshold values give rise to optimism that elimination of onchocerciasis is feasible, but the associated measures of parasite prevalence and density suggest that onchocerciasis can remain endemic at very low infection intensities. Endemicity at a low level is a risk factor for elimination strategies, and we point to the necessity of investigating these issues on the basis of breakpoints which refer to threshold conditions based on parasite prevalence and density.

[Filarial infestation in patients emanating from endemic area. 14 cases series presentation]

INTRODUCTION

The migration causes the emergence of new diseases in our environment. One of them is the filariosis which, due to the biologic cycle peculiarity, it's weird its appearance in pediatrics. This studio accomplishes a review of all the filariosis cases diagnosed the last years in an Unit specialized in Tropical Pediatrics Diseases.

MATERIAL AND METHODS

Retrospective analysis comprising 14 patients than were diagnosed with filariosis from 1995 to 2007 in the Pediatrics Unit of Carlos III Hospital (Madrid). They have been analyzed several variables to cope with clinic-epidemiological, therapeutics and evolutional characteristics.

RESULTS

All patients in the study came from Equatorial Guinea, their ages were between 3 and 15 years old. The isolated species were: 6 cases with O. volvulus, 8 with M. perstans and 2 with Loa-loa. The pruritus was the main symptom in the 71% of the cases. The eosinophilia was detected in the 78% of the patients, and the Loa-loa was the specie with higher figures. The 85% of the patients showed co-parasitation, being the intestinal the most frequent. The diagnostics was established by epidermic biopsy, microfilaremia detection, direct visualization and serology. The utilized drugs were: Mebendazole for the cases with M. perstans and Ivermectin or Dietylcarbamazine for the rest of the species. One child showed mixed filariosis. The cure was successful in the 8 cases that could be followed up.

CONCLUSIONS

We consider essential to execute a filariosis screening to every patient emanating from endemic area, especially to those with eosinophilia. The diagnostic in the childhood, even though it's difficult, it allows the prevention of the disease development, serious complications as blindness and break the parasite life cycle.

Successful interruption of transmission of Onchocerca volvulus in the Escuintla-Guatemala focus, Guatemala

BACKGROUND

Elimination of onchocerciasis (river blindness) through mass administration of ivermectin in the six countries in Latin America where it is endemic is considered feasible due to the relatively small size and geographic isolation of endemic foci. We evaluated whether transmission of onchocerciasis has been interrupted in the endemic focus of Escuintla-Guatemala in Guatemala, based on World Health Organization criteria for the certification of elimination of onchocerciasis.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted evaluations of ocular morbidity and past exposure to Onchocerca volvulus in the human population, while potential vectors (Simulium ochraceum) were captured and tested for O. volvulus DNA; all of the evaluations were carried out in potentially endemic communities (PEC; those with a history of actual or suspected transmission or those currently under semiannual mass treatment with ivermectin) within the focus. The prevalence of microfilariae in the anterior segment of the eye in 329 individuals (> or =7 years old, resident in the PEC for at least 5 years) was 0% (one-sided 95% confidence interval [CI] 0-0.9%). The prevalence of antibodies to a recombinant O. volvulus antigen (Ov-16) in 6,432 school children (aged 6 to 12 years old) was 0% (one-sided 95% IC 0-0.05%). Out of a total of 14,099 S. ochraceum tested for O. volvulus DNA, none was positive (95% CI 0-0.01%). The seasonal transmission potential was, therefore, 0 infective stage larvae per person per season.

CONCLUSIONS/SIGNIFICANCE

Based on these evaluations, transmission of onchocerciasis in the Escuintla-Guatemala focus has been successfully interrupted. Although this is the second onchocerciasis focus in Latin America to have demonstrated interruption of transmission, it is the first focus with a well-documented history of intense transmission to have eliminated O. volvulus.

The NGDO Co-ordination Group for Onchocerciasis Control

Since the beginning of the donation of Mectizan by Merck & Co., Inc., non-governmental development organizations (NGDO) have been actively involved in the mass distribution of this drug to control onchocerciasis. In 2006, the network of NGDO involved in onchocerciasis control assisted in the treatment of over 62 million people. The current strategy that is used for distribution in Africa, community-directed treatment with ivermectin (CDTI), is very well suited for integration with other health activities. NGDO have been the pioneers in integrating comprehensive eye care, insecticide-treated nets for malaria, the control of multiple 'neglected' tropical diseases, and vitamin-A supplementation. These expanded activities bring with them new challenges, which need to be addressed by all partners and where the NGDO will play an active role.

Operational lessons from 20 years of the Mectizan Donation Program for the control of onchocerciasis

The donation of ivermectin (Mectizan, Merck & Co., Inc.) to control onchocerciasis (river blindness) was established in 1987 and has since gradually expanded to provide for >570 million treatments cumulatively over the past 20 years. The Mectizan Donation Program (MDP) operates within a broad partnership in 33 endemic countries in need of mass treatment. Particular operational methods and tools are applied to facilitate ivermectin mass treatment. Drug management has been streamlined, including dosing, tablet size and packaging, and monitoring for adverse events. Much of the experience gained in the development of ivermectin mass treatment can be usefully applied in the recent broader perspective of control of neglected tropical diseases. The most important operational lessons of the MDP include: (i) the need to easily define the target population for treatment using rapid, non-invasive techniques; (ii) the value of a broad partnership; (iii) the great potential of working through community-directed treatment; (iv) the need to streamline all drug management aspects and (v) the importance of operations research to tackle new challenges.

Of mice, cattle, and humans: the immunology and treatment of river blindness

River blindness is a seriously debilitating disease caused by the filarial parasite Onchocerca volvulus, which infects millions in Africa as well as in South and Central America. Research has been hampered by a lack of good animal models, as the parasite can only develop fully in humans and some primates. This review highlights the development of two animal model systems that have allowed significant advances in recent years and hold promise for the future. Experimental findings with Litomosoides sigmodontis in mice and Onchocerca ochengi in cattle are placed in the context of how these models can advance our ability to control the human disease.

Blindness and poverty in India: the way forward

A few recent studies have shown that poverty is an exacerbating and often determining factor in the incidence of disabling conditions, including visual impairment. Recent estimates from the World Health Organization indicate that 90 per cent of all those affected by visual impairment live in the poorest countries of the world. India is home to one-fifth of the world's visually impaired people and therefore, any strategies to combat avoidable blindness must take into account the socio-economic conditions within which people live. This paper looks at the relationship between poverty and blindness in India and suggests strategies to address blindness prevention in a comprehensive manner.

The cys-loop ligand-gated ion channel gene family of Brugia malayi and Trichinella spiralis: a comparison with Caenorhabditis elegans

Nematode cys-loop ligand gated ion channels (CLGIC) mediate neurotransmission and are important targets for anthelmintics in parasitic nematodes. The CLGIC superfamily in nematodes includes ion channels gated by acetylcholine, gamma-amino butyric acid (GABA), glutamate, glycine and 5-HT. The macrocyclic lactones and the nicotinic agonists are important groups of anthelmintics that target the glutamate gated chloride channels and the nicotinic acetylcholine receptors, respectively. The model organism Caenorhabditis elegans has the most diverse families of cys-loop LGIC known in any organism. Many parasitic nematodes have homologues of C. elegans receptors but to date no genome wide investigations have been done. The genome sequencing projects of Brugia malayi (clade III) and Trichinella spiralis (clade I) have allowed us to characterise the CLGIC families in these species. Although the main groups of CLGICs targeted by anthelmintics are represented in both the nematode genomes investigated here, the CLGIC family is much smaller in B. malayi and T. spiralis, suggesting that care must be taken when using C. elegans as a model organism for distantly related nematodes.