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PubMed1996

Eye disease in an onchocerciasis-endemic area of the forest-savanna mosaic region of Nigeria.

In a forest-saving mosaic zone of south-eastern Nigeria endemic for onchocerciasis, we identified eye disorders in 65.5% of a randomly selected population sample. Onchocerciasis-related eye disease was present in 13.7% of the study sample and constituted 21% of the total number of eye disorders. A total of 78 (33.2%) of 235 subjects with visual impairment had onchocerciasis-related eye lesions, and of 35 who were blind in both eyes, onchocerciasis-induced eye disease was the cause in 28 (80%). The prevalence of bilateral blindness from all causes in the study area was 4.1%, while that from onchocerciasis-related causes was 3.3%. The commonest onchocerciasis-induced lesions that were responsible for visual impairment and blindness were choroidoretinitis and optic nerve disease. Sclerosing keratitis, an important causative lesion in onchocerciasis-endemic savanna regions, was encountered only one. Eye disease is therefore an important feature of onchocerciasis in the forest-savanna mosaic areas of Nigeria and should be borne in mind when planning and executing control programmes.

Adolescent↗

PubMed1996

Immunoregulation in onchocerciasis: predominance of Th1-type responsiveness to low molecular weight antigens of Onchocerca volvulus in exposed individuals without microfilaridermia and clinical disease.

Chronic and generalized onchocerciasis is associated with suppression of the parasite-specific cellular responsiveness, while exposed individuals without parasitological and clinical evidence of infection (endemic normals) display prominent cellular reactivity to Onchocerca volvulus antigens (OvAg). In order to identify those parasite antigens which may account for this differential cellular responsiveness, total adult worm-derived OvAg were fractionated by means of preparative SDS-PAGE and blot-elution into 22 antigen fractions of continuously decreasing molecular weight. Peripheral blood mononuclear cells (PBMC) from microfilariae (mf)-positive onchocerciasis patients (n = 18) proliferated weakly in response to all OvAg fractions. In contrast, in vitro reactivity of PBMC from endemic normals (n = 9) was depressed in response to OvAg of mol. wt 200-30 kD only, while antigens of mol. wt < 30 kD induced vigorous proliferation in these individuals compared with the microfilaridermic patients (P < 0.05). Highest proliferative reactivity of cells from endemic normals was observed in response to OvAg of mol. wt 15-11 kD. Furthermore, these low mol. wt antigen fractions induced substantial production of IL-2 and interferon-gamma (IFN-gamma) in PBMC from endemic normals, but not in those from onchocerciasis patients. Cells from individuals of both groups secreted similar amounts of IL-5 in response to all OvAg fractions, with highest production again being induced by low mol. wt OvAg. In contrast, PBMC from onchocerciasis patients clearly produced more IL-10 than did cells from endemic normals. This augmented IL-10 production by PBMC from mf-positive individuals was not only observed after stimulation with OvAg fractions, but was measured in unstimulated control cultures as well. IFN-gamma-specific mRNA in antigen-stimulated PBMC from endemic normals appeared to be more prominent than in cells from onchocerciasis patients. However, mRNA transcripts of IL-10 and IL-13 were clearly present in patients, but were absent or inconsistently observed in endemic normals. Our results suggest that vigorous Th1-type cellular responsiveness encountered in endemic normals is restricted to low mol. wt antigens of O. volvulus, while such reactivity will not be present in mf-positive individuals. Furthermore, spontaneous production of high levels of IL-10 in onchocerciasis patients is likely to suppress Th1-type immunity, and thus may favour manifestation of chronic onchocerciasis. These traits of cellular immunity may contribute to the differential outcome of O. volvulus infection, the manifestation of clinical disease, and may also regulate the build up of acquired immunity in humans.

Adolescent↗

PubMed2005

Geographical patterns of onchocerciasis in southern Venezuela: relationships between environment and infection prevalence.

Onchocerciasis is a chronic filarial infection transmitted by Simulium flies that has a focal geographical distribution in Latin America. The southern Venezuelan focus has a gradient of endemicity that includes the largest number of hyperendemic communities in the continent, many of them in remote forest and mountainous areas, where it is an important public health problem among the Yanomami indigenous population. The recent introduction of Geographical Information Systems (GIS) tools and a landscape epidemiology approach for study of vector borne diseases is helping to understand relationships between environment and transmission dynamics of onchocerciasis. Striking differences in the transmission dynamics of onchocerciasis between different river courses were detected. A significant relationship between onchocerciasis and temperature was also demonstrated. The geologic substrate, kind of landscape and vegetation seemed also to influence the transmission of onchocerciasis. In the Venezuelan Amazon, different kinds of landscapes associated with distinctive vector species, show different intensities of transmission of onchocerciasis. In this sense, landscape analysis aided by GIS, may prove to be a useful tool for better identification of the spatial distribution of onchocerciasis risk in the Orinoco basin.

Altitude↗

PubMed1990

Human onchocerciasis--an overview of the disease.

The general characteristics of Onchocerca volvulus infection and its transmission are outlined in this overview of human onchocerciasis. The pathogenic role of the microfilariae, producing lesions of the skin, lymphatic system, eye and deep organs, are described, along with the main clinical manifestations of the disease. The global prevalence and distribution of onchocerciasis are given. Best estimates in 1985 gave 86 million persons at risk, 17.8 million infected, 336,400 blind and a like number suffering from severe visual impairment. The vast majority was in Africa. The impact of onchocerciasis on communities in the Sudano-Guinean savanna zone of Africa is outlined, emphasizing the very high blindness rates and the increased mortality among the blind. Communities so affected cannot remain economically viable. They are forced to desert their villages and the fertile land near rivers. The background to the establishment of the Onchocerciasis Control Programme in West Africa (OCP) is given and the successful 10-year results of this campaign, which is based on prolonged, regular Simulium larviciding, are outlined. In the context of the future of the OCP and of the control of onchocerciasis elsewhere in the world, the need for improved chemotherapy is discussed. The prospects for large-scale suppressive therapy have greatly improved following the registration of ivermectin in 1988 for use in human onchocerciasis. The potential and possible uses of this drug, as a single-dose, non-toxic microfilaricide, which excites very little Mazzotti reaction and has a prolonged microfilarial suppressant action, are discussed. It is considered that an effective non-toxic macrofilaricide is still a prime need for onchocerciasis control.

Africa↗

PubMed1993

Autoimmunity and filariasis. Autoantibodies against cytoplasmic cellular proteins in sera of patients with onchocerciasis.

Onchocerciasis or "river blindness" is a vector-borne tropical disease resulting from infection with the filarial nematode Onchocerca volvulus. Disease manifestations include dermatitis, rheumatic complaints, and blindness. Recent findings have suggested an autoimmune etiology for the occurrence of chorioretinopathy, a disease of the eye which together with sclerosing keratoconjunctivitis is responsible for approximately 400,000 onchocerciasis-related cases of blindness. The identification of onchocerciasis as an important cause of tropical rheumatism prompted us to evaluate serologically the presence of systemic autoimmune disease in onchocerciasis patients and local controls from a hyperendemic area in Sierra Leone. In both groups there was a marked autoimmune response against cytoplasmic non-RNA-associated proteins consisting of autoantibodies against five major Ag with respective m.w. of 35, 51, 64, 83, and 110 kDa. These five proteins are novel autoantigens that could be distinguished from calreticulin, the human homologue of the onchocercal Ag RAL-1, and known autoantigens such as the 50-kDa La/SS-B or 52- and 60-kDa Ro/SS-A proteins by immunoblotting and ELISA assays. Furthermore, autoantibody reactivity against calreticulin was significantly higher in O. volvulus-infected individuals than in endemic controls. Autoantibody reactivity against the five major autoantigens, anti-calreticulin reactivity, and antibody reactivity against the 65-kDa arthritis-associated mycobacterial heat shock protein were intercorrelated as parts of an onchocerciasis-associated autoimmune response. The implication of autoimmunity in the disease pathogenesis of onchocerciasis could have important consequences for future research on therapeutical regimens, pathogenetic mechanisms, and serological diagnosis of onchocerciasis.

Antibodies, Antinuclear↗

PubMed1993

Onchocerciasis in field workers at Baya Farm, Teppi Coffee Plantation Project, southwestern Ethiopia: prevalence and impact on productivity.

A survey of onchocerciasis in male field workers was conducted in Baya Farm, Teppi Coffee Plantation Project, southwestern Ethiopia, in order to determine the prevalence rate of onchocerciasis in that population and to measure the effect of the disease on work productivity. A total of 196 study subjects were examined both clinically and parasitologically. Parasitological diagnosis was based on bilateral skin biopsies from the calf, buttock, and scapula. It was found that the prevalence rate of onchocerciasis (82.7%) and the intensity of infection were very high. No study subject had any detectable visual impairment, and other chronic manifestations were few. Based on a twelve month retrospective review of labour cards, workers with onchocerciasis were significantly more likely to be absent from work due to illness and other reasons, and earned significantly less wages, than workers without onchocerciasis, thus suggesting that non-blinding onchocerciasis has a negative impact on work productivity.

Adult↗

PubMed1984

The economics of blindness prevention in Upper Volta under the Onchocerciasis Control Program.

This paper proposes a new approach to the economics of blindness prevention under the Onchocerciasis Control Program in Upper Volta. It differs from previous economic analyses of onchocerciasis control in three important respects. First, it uses empirical data as the basis of an estimate of the epidemiological effectiveness of the intervention. Second, it focuses on the prevention of permanent disability and premature death due to onchocercal blindness as the major health improvement attributable to onchocerciasis control. Third, it emphasizes cost-effectiveness rather than cost-benefit analysis. This limitation is imposed by the difficulty of undertaking a comprehensive assessment of the benefits of onchocerciasis control. In particular, the extent to which control of partial visual impairment and infection without ocular involvement would increase the effective supply of labor, and also the extent to which control would increase the effective supply of land by inducing new settlement in the river valleys, have not been clearly established. The cost-effectiveness approach is limited because it foregoes the opportunity provided by cost-benefit analysis to compare the relative desirability of investing in onchocerciasis control with alternative investments in other sectors. However, it does permit useful judgments to be made about the relative efficiency of allocating scarce resources to onchocerciasis control compared to other possible investments within the health sector. For this purpose, an illustrative comparison is made with estimates of the cost-effectiveness of measles immunization.

Blindness↗

PubMedDate not supplied

Relationship between onchocerciasis and epilepsy: a matched case-control study in the Mbam Valley, Republic of Cameroon.

Studies conducted during the past 10 years to investigate the possible relationship between onchocerciasis and epilepsy have led to contradictory results. In 1991-92 and 2001 we investigated 14 villages in central Cameroon to evaluate the relationship, at the community level, between the prevalence of epilepsy and the endemicity level of onchocerciasis. A case-control study compared the microfilarial loads of 72 epileptic and 72 non-epileptic individuals, matched according to sex, age, and village of residence. The prevalence of epilepsy and the community microfilarial load (CMFL) were closely related (P < 0.02), and the case-control study demonstrated that the microfilarial loads (microfilariae per snip) in the epileptic group (arithmetic mean = 288, median = 216) were significantly higher (P < 10(-4)) than in the control group (arithmetic mean = 141, median = 63). The results strongly support the existence of a link between onchocerciasis and epilepsy. The fact that such a relationship has not been found recently in some other West and Central African areas is probably due to the lowered endemicity of onchocerciasis following vector- and ivermectin-related control measures applied over the past 5-25 years. The socio-economic and demographic impact of onchocerciasis-related epilepsy should be evaluated, and taken into account as part of all onchocerciasis control programmes.

Adolescent↗

PubMed2006

Control of onchocerciasis.

Onchocerciasis is a filarial infection which causes blindness and debilitating skin lesions. The disease occurs in 37 countries, of which 30 are found in Africa (the most affected in terms of the distribution and the severity of the clinical manifestations of the disease), six in the Americas and one in the Arabian Peninsula. The latest WHO Expert Committee on Onchocerciasis estimated that in 1995 around 17.7 million persons were infected, about 270,000 of whom were blind and another 500,000 severely visually impaired. The disease is responsible for 1 million DALYs. Eye disease from onchocerciasis accounts for 40% of DALYs annually although severe skin disease is also recognized as of public health significance. Great progress has been made in the last thirty years in the control of onchocerciasis, both in Africa and the Americas, and this progress has been due largely to international public-private partnerships, sustained funding regional programmes, and new tools and technology. Landmarks in the global control of river blindness include the significant success of the Onchocerciasis Control Programme of West Africa (1975-2002), and the donation of ivermectin (Mectizan) by Merck & Co. Inc., in 1988, a medicine that is distributed to millions free of charge each year. Future major technical challenges of onchocerciasis control include ivermectin mass administration in areas co-endemic for the parasite Loa loa in the light of possible severe adverse reactions, ivermectin treatment in hypoendemic areas hitherto excluded from African control programmes, sustainability of ivermectin distribution, post-control surveillance for recrudescence detection, surveillance for emergence of resistance, and decisions of when to stop mass ivermectin treatments. There is the need to develop the appropriate information systems and diagnostic tools to help in accomplishing many of these tasks. A search for a second-line treatment or as an additional drug to ivermectin as well as a search for a macrofilaricide are issues that need to be addressed in the future.

Africa↗

PubMed1997

Onchocerciasis: clinical presentation and host parasite interactions in patients of southern Sudan.

BACKGROUND: Onchocerciasis, an infection by the filarial nematode Onchoverca volvulus, is widely distributed in tropical Africa and of great dermatologic interest. This study analyses the dermatologic presentation and tries to determine the correlations between clinical disease and host parasite interactions in onchocerciasis patients of the Southern Sudan. METHODS: We performed clinical and histopathologic investigations in patients with onchocerciasis in the Wau District, Bahr el Ghazal Province, Southern Sudan. As well as a detailed clinical skin examination, skin biopsies were taken, processed, and investigated for type and degree of host tissue response. Parasitologic, clinical, and histopathologic findings were evaluated. RESULTS: Onchocerciasis appears with a variety of severe skin lesions. Central is a pruritic rash. Long-standing cases develop extensive pigmentary changes and impressive signs of skin tissue exhaustion. Cellular host tissue responses to degenerating skin microfilariae seem to play a key role in the development of skin pathology. The degree of host response appears to be inversely proportional to the host's microfilarial load. CONCLUSIONS: Onchocerciasis represents a health problem of great dermatologic importance in Southern Sudan. The study results demonstrate clinical variations in onchocerciasis and provide support for the existence of a disease spectrum.

Adolescent↗

PubMedDate not supplied

Global priorities in the control of onchocerciasis.

Onchocerciasis is a major blinding disease. Appropriately, the World Health Organization, in cooperation with other United Nations agencies, supports two large-scale onchocerciasis programs. First, the Special Programme for Research and Training in Tropical Diseases has provided major support for much of the recent research on onchocerciasis. Second, the Onchocerciasis Control Programme is an ambitious, service-oriented effort to eliminate onchocerciasis as a public health problem in the Volta River basin area of West Africa. Initially, the latter program focused on vector control measures; recently, however, it has launched a major chemotherapy development initiative. Taken together, these two programs provide comprehensive support for the development of chemotherapy and vector control measures. However, in the absence of another integrated research program, there is a need to strengthen the available support for research into the immunologic aspects of onchocerciasis.

Filariasis↗

PubMed1994

Evaluation of Onchocerca volvulus-specific IgG4 subclass serology as an index of onchocerciasis transmission potential of three Gabonese villages.

The major objective of this study was to evaluate the usefulness of IgG4 ELISA and Western blot analysis, using a crude extract of Onchocerca volvulus adult worms as antigens, for diagnosing onchocerciasis in a Gabonese paediatric population with mixed filarial infections. The subjects had loaisis, streptocercosis or mansonellosis in addition to onchocerciasis. Control sera from loaisis or mansonellosis subjects residing outside the endemic zone were used to provide the cut-off point for positive results. The IgG4 ELISA had a specificity of 96% but a lower sensitivity of 78.7%. It detected 25 onchocerciasis cases out of 65 individuals who were negative on parasitological examination. Furthermore, the ELISA provided a more accurate picture of onchocerciasis transmission in a village with very low skin microfilarial load. A 27.5-kD antigen was identified on Western blots as a marker of onchocerciasis. The paediatric population provided a reliable window for assessing the parasitologic and serologic parameters in the three villages with disparate levels of onchocerciasis transmission.

Adolescent↗

PubMed2006

Towards the elimination of onchocerciasis.

Human onchocerciasis is a severely disabling filarial disease that is endemic in 28 African countries, six Latin American countries and Yemen. The disease causes a high burden of blindness and visual loss, along with itching and other severe dermal manifestations. It constitutes a significant obstacle to socio-economic development in highly endemic riverine areas, where the Simulium blackflies that act as vectors breed. Onchocerciasis has been subject to control efforts for more than 50 years, initially mainly through vector control but since 1988, with free access to ivermectin (Mectizan), also through large-scale chemotherapy. The Onchocerciasis Control Programme in West Africa operated successfully from 1974 to 2002 in 11 countries, covering the worst savannah foci of the disease through vector control and, in its later stages, also through ivermectin distribution. The African Programme for Onchocerciasis Control was established in 1995, to cover the remaining endemic areas in Africa, with the sustainable annual distribution of ivermectin by 2010 its main goal. Meanwhile, the Onchocerciasis Elimination Program for the Americas is making rapid progress in the virtual regional elimination of the disease through ivermectin distribution, which is achievable primarily because the vectors in the western hemisphere are less efficient than those elsewhere. The global elimination of onchocerciasis as a public-health problem is now within reach but this will require long-term strategies to secure the great gains made so far, through ivermectin treatment and local vector control. Research is needed to define the optimal approaches with the existing tools and to intensify the development of alternative strategies, such as macrofilaricidal drugs for wide-scale use.

Africa↗

PubMed2000

Onchocerciasis presenting with lower extremity, hypopigmented macules.

Onchocerciasis, or river blindness, is a parasitic infection caused by the filarial nematode, Onchocerca volvulus. It infects 18 million people worldwide, but is rarely seen in the United States. It is one of the leading causes of blindness in the developing world. Although onchocerciasis is also known as river blindness, it is not just a disease of the eyes, but rather a chronic multisystem disease. Clinically, onchocerciasis takes three forms: 1) eye disease; 2) subcutaneous nodules; and 3) a pruritic hypopigmented or hyperpigmented papular dermatitis. We present an 18-year-old African female with a 5-year history of asymptomatic, hypopigmented, slightly atrophic macules on her anterior tibiae. Pathology revealed a scant perivascular inflammatory infiltrate with mononuclear cells, eosinophils, and rare microfilariae in the papillary dermis. Ivermectin is the treatment of choice for onchocerciasis and was initiated in this patient. We present this interesting patient with onchocerciasis to expand our differential of hypopigmented macules, especially in the African population. In addition, we discuss both the diagnosis and the treatment of onchocerciasis in expatriate patients living in nonendemic areas.

Adolescent↗

PubMed1990

Humoral autoimmune response against S-antigen and IRBP in ocular onchocerciasis.

Autoimmune mechanisms are thought to play a role in the pathogenesis of the chorioretinal changes in ocular onchocerciasis. In this study, the involvement of autoimmunity against retinal antigens in developing chorioretinitis was investigated. Serum levels of autoantibodies, directed against human S-antigen and interphotoreceptor retinoid-binding protein (IRBP), were determined in patients with onchocerciasis (n = 46) and endemic controls (n = 38) from Sierra Leone with the use of an enzyme immunoassay. In both groups high levels of anti-human S-antigen and IRBP antibodies were detected. No relationship could be demonstrated between the antiretinal antibody level and the occurrence of chorioretinitis in onchocerciasis. The levels of both anti-human S-antigen and IRBP antibodies were significantly higher in patients with onchocerciasis compared with endemic controls (P less than 0.001). Cross-reactivity of antiretinal antibodies with parasitic antigens could not be demonstrated as a possible explanation for the higher levels in patients with onchocerciasis. No correlation was found between the levels of antibodies of different classes against the crude Onchocerca volvulus, the egg antigen, or the microfilariae and the antiretinal antibody levels. Furthermore, in a panel of 13 different monoclonal antibodies directed against O. volvulus, only one showed a slight anti-human IRBP reactivity and none reacted with S-antigen. The immune response against the two retinal antigens investigated was not specific for onchocerciasis because high antibody levels were also found in patients with Bancroftian filariasis from Papua, New Guinea, and Surinam.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Cell-mediated and humoral immune responses to BCG and rubella vaccinations and to recall antigens in onchocerciasis patients.

In seven Liberian villages of different endemicity for onchocerciasis 629 persons were tested for tuberculin reactions using 5 i.u. purified protein derivative or old tuberculin. No correlation between infection with Onchocerca volvulus and reactivity to tuberculin was detected on a community level, but a direct comparison of results of infected and non-infected individuals in two neighboring villages revealed a lower responsiveness in persons with onchocerciasis. The conversion rate three months after BCG vaccination was significantly lower in children with onchocerciasis (48%) than in controls (85%). The possible impact of this finding on the efficacy of BCG vaccinations is discussed. Girls aged 2-16 years were screened for rubella antibodies using a latex agglutination test. Sera from 74 girls, who showed no antibodies, were examined before and four months after rubella vaccination by haemagglutination-inhibition-test and haemolysis-in-gel-test. No difference in the humoral immune response of girls with or without onchocerciasis was found. Seroconversion rates were 98% and 100%. Delayed cutaneous hypersensitivity (DCH) to seven ubiquitous recall antigens was tested in 147 persons infected with O. volvulus and compared to the results of 142 non-infected controls. A reduced responsiveness was seen in persons with onchocerciasis, the difference being greatest in young children 2-7 years of age. In connection with the results of tetanus vaccinations reported earlier, these findings verify the existence of a reduced in vivo responsiveness of cell-mediated immunity to non-specific antigens in onchocerciasis in the rain forest of West Africa. Humoral immune responses however appeared to be unaffected.

Adolescent↗

PubMed1986

Onchocerciasis in Sudan: the distribution of the disease and its vectors.

The distribution of onchocerciasis and its vectors in Sudan has been reviewed with special emphasis on the hyperendemic foci where there is serious visual handicap caused by the disease. These blinding foci lie primarily in the south-west of the country, along the rivers flowing north and east from the borders with Central African Republic and Zaire, though at least one such focus is known from the eastern part of the country close to the Ethiopian border. In the blinding foci, often small villages localized to short stretches of the rivers, ocular onchocerciasis is as severe as that found in any other African foci. Only the S. damnosum s.l. species complex has been implicated in disease transmission and only the two dangerous, morphologically similar, savanna cytospecies, S. damnosum s.s. and S. sirbanum, have been identified from breeding sites close to known onchocerciasis foci. Near to the Uganda and Zaire borders it is very likely that other, less anthropophilic, cytospecies occur. Different Onchocerca-Simulium complexes (different strains of parasite with different pathogenicities transmitted by different vector species) may be responsible for the different severities of disease found in the 3 main areas of onchocerciasis in North, East and South-West Sudan. The localized, focal distribution of the communities seriously blinded by onchocerciasis, suggests that a strategy of tackling the disease on a focus basis may prove optimal. A control scheme, planned to treat all the vector breeding sites with insecticide, as in West Africa, would receive extensive invasion from the Zaire/Congo River Basin and the headwaters of the White and Blue Niles in neighbouring countries. While some foci are situated beside major river rapids, with vector breeding only controllable by regular insecticide treatments, several foci have been identified as lying close to removable man-made objects which provide excellent breeding sites at certain water levels e.g. causeways. The destruction of such breeding sites should be considered since localized vector control may produce substantial reductions in onchocerciasis transmission.

Animals↗

PubMed1994

[Onchocerciasis control program in West Africa: socioeconomic development and risk of recrudescence of transmission. 2. Experimental study of the transmission of Onchocerca volvulus strains from Southwestern Sierra Leone by Simulium yahense and Simulium squamosum].

The movements of human populations towards the mining wealth of the northern parts of Sierra Leone are favorable to a high contact rate between onchocerciasis patients coming from the south-western area of this country and the vector species Simulium yahense and Simulium squamosum which assume the essential of onchocerciasis transmission in the above-mentioned mining area. In fact, the Onchocerca volvulus strains concerned by this contact seem to be more pathogenic than those locally transmitted. In order to assess the danger it could represent for the Onchocerciasis Control Programme in West Africa, we carried out the experimental study of transmission which may result from this contact when more or less infected onchocerciasis patients are involved. The results indicated that this transmission by S. yahense may reach high proportions only when heavily infected onchocerciasis patients are implicated. We took also notice of the low capacity of S. squamosum to transmit the O. volvulus strains from the south-western Sierra Leone, irrespective of the microfilarial load of patients. Thus, in the most favorable conditions of a high parasite-vector contact of the study, involvement of S. yahense and onchocerciasis patients with high skin microfilarial loads is the only occurrence to which a high risk of intensive transmission may be related. The authors consider that the probability of such a risk occurring will be drastically reduced, due to the considerable decrease of skin microfilarial loads in human communities which regularly have the advantage of ivermectin (Mectizan) mass treatments.

Animals↗