Infectivity of Simulium damnosum s.l. and therapeutic coverage of ivermectin distribution 10 years post treatment around Owena Dam, Ondo state, Nigeria

ABSTRACT Background: Studies related to infectivity status of insect vectors are seen as necessities in understanding the epidemiology of vector-borne diseases and planning effective control measures. This study assessed the infectivity ofSimulium damnosum s.l. around Owena River as well as evaluated therapeutic coverage of Ivermectin distribution in the area. Method: Human landing sampling method was used to collect adult flies on human attractants from 07:00 to 18:00 for two consecutive days a month for three months (July 2016 - September 2016). Parity assessment was conducted to determine the age of fly populations. Parous flies were further dissected to detect the presence or absence ofOnchocerca larvae. Biting rates and transmission potentials were calculated using standard methods. A quantitative survey was carried out to determine the therapeutic coverage and compliance to ivermectin treatment for the control of Onchocerciasis in the study area using standard household coverage questionnaires. Results: A total of 914 adult female flies were collected during the study period. The daily biting rate (DBR) varied from 146 fly per man day (FMD) in July to 162.5 FMD in August. The monthly biting rate (MBR) was lowest in September (2170 bites per man per month) but highest in August (3358.3 bites per man per month). MBD ranged from 13.23 fly per man hour (FMH) in July to 14.77 FMH in August. The results indicated that the majority of the flies collected at the sampling points were nulliparous [685 (74.95%)] while others were parous [229 (25.05%)]. The biting activity of the flies showed a marked decrease in population in August compared to July which later increased in September. Infection rates varied from 2 (0.7%) in July to 7 (2.2%) in August while the infectivity rate during the study ranged from zero (July and September) to 3 (1.0%) in August. Conclusion: Despite the years of treatment of onchocerciasis in Owena community, there were still some infective flies capable of transmitting O. volvolus. This could be due to the low rate of therapeutic coverage as a result of non-compliance in the community for various reasons earlier stated.

New records of Mansonella ozzardi: a parasite that is spreading from the state of Amazonas to previously uninfected areas of the state of Acre in the Purus River region

Mansonella ozzardi infections are common in the riverside communities along the Solimões, Negro and Purus Rivers in the state of Amazonas (AM). However, little is known about the presence of this parasite in communities located in regions bordering AM and the state of Acre. The prevalence rate of M. ozzardi infections was determined in blood samples from volunteers according to the Knott method. A total of 355 volunteers from six riverine communities were enrolled in the study and 65 (18.3%) were found to be infected with M. ozzardi. As expected, most of the infections (25%) occurred in individuals involved in agriculture, cattle rearing and fishing and an age/sex group analysis revealed that the prevalence increased beginning in the 40-50-years-of-age group and reached 33% in both sexes in individuals over 50 years of age. Based on the described symptomatology, articular pain and headache were found to be significantly higher among infected individuals (56 and 65% prevalence, respectively, p < 0.05). Sera from volunteers were subjected to ELISA using a cocktail of recombinant proteins from Onchocerca volvulus to evaluate the specificity of the test in an endemic M. ozzardi region. No cross-reactions between M. ozzardi-infected individuals and recombinant O. volvulus proteins were detected, thus providing information on the secure use of this particular cocktail in areas where these parasites are sympatric.

Prevalence of Mansonella ozzardi among riverine communities in the municipality of Lábrea, State of Amazonas, Brazil / Prevalências de Mansonella ozzardi entre comunidades ribeirinhas do município de Lábrea, Estado do Amazonas

INTRODUCTION: Estimate the prevalence of Mansonella ozzardi infection and calculate the parasitic infection rate (PIR) in simuliid black flies in the municipality of Lábrea, State of Amazonas, Brazil. METHODS: Prevalence was measured using the thick blood smear method collected from the fingers and was related to age, sex and occupation. Simuliidae were collected with a suction apparatus, then stained with hematoxylin and dissected to verify the PIR. RESULTS: The average prevalence rate of M. ozzardi among the 694 individuals examined was 20.7 percent. Infection was higher in men (27.6 percent) than in women (14.3 percent) (p < 0.001) and occurred in most age groups, with the highest prevalence in the following age groups: 38-47 (40 percent), 48-57 (53.1 percent) and >58 (60.5 percent). The highest prevalence rates were observed in the retired (64 percent), followed by farm workers (47.1 percent). Infection by M. ozzardi was only identified in Cerqueirellum amazonicum (Simuliidae) with a PIR of 0.6 percent. CONCLUSIONS: This study showed a high prevalence of M. ozzardi in the riverine communities of Lábrea due to the lack of policies regarding the treatment of microfilaremic individuals in the region and an abundance of competent vectors for M. ozzardi.

INTRODUÇÃO: Estimar as prevalências de Mansonella ozzardi, e calcular a taxa de infecção parasitária nos simulídeos no município de Lábrea, Estado do Amazonas. MÉTODOS: As prevalências foram obtidas através do método de gota espessa a partir do sangue coletado da polpa digital e foram relacionadas com a idade, sexo e ocupação. Os simulídeos foram coletados com capturador de sucção, posteriormente foram corados com hematoxilina e dissecados para se obter a taxa de infecção parasitária. RESULTADOS: A prevalência de M. ozzardi entre as 694 pessoas examinadas foi de 20,7 por cento. A infecção foi maior nos homens (27,6 por cento) do que nas mulheres (14,3 por cento) (p < 0,001) e ocorreu na maioria das faixas etárias com maiores prevalências nos indivíduos entre 38-47 (40 por cento), 48-57 (53,1 por cento) e >58 (60,5 por cento) anos. As maiores prevalências foram observadas nos aposentados (64 por cento) e agricultores (47,1 por cento). Somente Cerqueirellum amazonicum (Simuliidae) foi encontrado infectado com M. ozzardi com uma taxa de infecção parasitária de 0,6 por cento. CONCLUSÕES: Este trabalho mostra elevadas prevalências de M. ozzardi nas comunidades ribeirinhas de Lábrea devido à ausência de políticas de tratamento dos microfilarêmicos na região e a abundância de vetores competentes.

Mansonella ozzardi in Amazonas, Brazil: prevalence and distribution in the municipality of Coari, in the middle Solimões River

This study investigated some epidemiological aspects of the Mansonella ozzardi in municipality of Coari, Amazonas. Clinical symptoms were correlated with the filarial infection and the parasitic infection rates (PIR) were estimated in simuliid vectors. The general M. ozzardi human prevalence rate was 13.3 percent (231/1733), of which 10.2 percent (109/1069) were from the urban area and 18.4 percent (122/664) from the rural area. The prevalence rates were higher in men (14.5 percent urban and 19.7 percent rural) than in women (6.7 percent urban and 17.2 percent rural) and occurred in most age groups. The indices of microfilaremics were higher in people > 51 years old (26.9 percent urban and 61.5 percent rural). High prevalence rates were observed in retired people (27.1 percent urban area), housewives and farmer (41.6 percent and 25 percent, respectively, in rural area). The main clinical symptoms were joint pains and sensation of leg coldness. Only Cerqueirellum argentiscutum (Simuliidae) transmits M. ozzardi in this municipality (PIR = 5.6 percent urban and 7.1 percent rural). M. ozzardi is a widely distributed parasitic disease in Coari. Thus, temporary residency in the region of people from other localities involved with the local gas exploitation might be a contributing factor in spreading the disease.

Ocorrência da Mansonella ozzardi (Nematoda, Onchocercidae) em comunidades ribeirinhas do rio Purus, Município de Boca do Acre, Amazonas, Brasil / Occurrence of Mansonella ozzardi (Nematoda, Onchocercidae) in riverine communities of the Purus river, Boca do Acre municipality, Amazonas State, Brazil

Este estudo teve o objetivo de estimar as prevalências de Mansonella ozzardi e calcular taxa de infecção parasitária nos simulídeos. O trabalho foi realizado em comunidades ribeirinhas do rio Purus, Boca do Acre, Amazonas, Brasil. As prevalências foram obtidas por meio do método de gota espessa de sangue obtido por porção digital. Os simulídeos coletados foram dissecados para estimar a taxa de infecção parasitária. A prevalência de M. ozzardi foi de 27,3 por cento (282/77). Foram observadas maiores prevalências nos homens (31,97 por cento) que nas mulheres (22,22 por cento), nos agricultores (48 por cento) e nos indivíduos entre: 38-47 (60 por cento), 48-57 (66,66 por cento) e 58-67 (75 por cento). A microfilaremia foi maior nos indivíduos entre 58-67 anos (média = 58,41mf/40µL), sexo masculino (41,44mf/40µL) e nos agricultores (49,94mf/40µL). Somente o simulídeo Cerqueirellum amazonicum foi encontrado infectado com taxa de infecção parasitária de 0,98 por cento.

The study aimed to estimate the prevalence of Mansonella ozzardi and calculate the parasitic infection rate in simuliid blackflies. The research was conducted in communities on the Purus River, Boca do Acre municipality, Amazonas State, Brazil. Prevalence was measured using the thick smear method. Captured blackflies were dissected to verify the parasitic infection rate. M. ozzardi prevalence was 27.30 percent (77/282). The study showed higher prevalence in men (31.97 percent) than women (22.22 percent), farmers (48.99 percent), and individuals in the 38-47 (60.00 percent), 48-57 (66.66 percent), and 58-67-year age brackets (75.00 percent). Microfilaremia was higher in individuals 58 to 67 years of age (average= 58.41mf/40µl), men (41.44mf/40µl), and farmers (49.94mf/40µl). Only the simuliid Cerqueirellum amazonicum was found infected with a parasitic infection rate of 0.98 percent.

Mansonella ozzardi in Brazil: prevalence of infection in riverine communities in the Purus region, in the state of Amazonas

This study was undertaken to investigate the prevalence of Mansonella ozzardi infection and to estimate the parasitic infection rate (PIR) in simuliid black flies in the municipality of Pauini, Amazonas, Brazil. We used thick blood films to examine 921 individuals in 35 riverine communities along the Pauini and Purus Rivers. Simuliids were caught in several communities. Flies were identified, stained with haematoxylin and dissected. Overall, 44 (24.86 percent) of 177 riverines were infected in communities on the Pauini River and 183 (24.19 percent) of 744 on the Purus. The prevalence was higher in men (31.81 percent and 29.82 percent) than in women (17.98 percent and 19.18 percent) and occurred in most age groups. The prevalence increased sharply in the 28-37 (50 percent and 42.68 percent) age group and increased in the older age classes. The highest prevalence was in farmers (44 percent and 52.17 percent, respectively) in the Pauini and Purus Rivers. Only Cerqueirellum amazonicum (Simuliidae) transmits M. ozzardi in this municipality, and we found a PIR of 0-8.43 percent and infectivity rate of 0-3.61 percent. These results confirm that rates of M. ozzardi infection are high in Pauini and suggest that its prevalence may be far greater than has been previously reported due to the absence of a program for treating the population.

Transmission dynamics of Simulium damnosum in rural communities of Akwa Ibom State, Nigeria.

BACKGROUND & OBJECTIVES: Onchocerciasis is endemic in some parts of Akwa Ibom State, Nigeria. This study describes the entomological parameters of transmission in three rural communities of Akwa Ibom State, prior to ivermectin intervention in 2004. METHODS: Blackflies were caught using human bait and 90% of the flies were dissected for parity. All parous flies were further dissected for the presence of filaria larvae. Monthly and annual biting rate, and transmission potential were calculated using standard methods. RESULTS: A total of 4296 adult Simulium damnosum were caught on human bait, 4119 were dissected of which 208 (5.1%) were infected with Onchocerca volvulus larvae. Transmission parameters varied significantly (p < 0.05) in the three villages. Annual biting rates, ranged from 9490 to 11,218 bites per person per year. The annual transmission potential ranged from 131 to 189 infective larvae per person per year, monthly biting rate and monthly transmission potential varied significantly (p < 0.05) in the three villages. Transmission was highly seasonal occurring during the peak of rainy season from August to October. There was no transmission during the dry periods--November to March, and the early rainy periods--April to May. The diurnal biting activity of the fly exhibited a bimodal pattern with a morning peak (0900-1000 hrs) and a more marked evening peak (1600-1700 hrs). INTERPRETATION & CONCLUSION: The results indicate that there is a temporal and spatial variation in the transmission dynamics of S. damnosum in the study area.

Population dynamics of onchocerca volvulus microfilariae in human host after six years of drug control.

BACKGROUND & OBJECTIVES: Mass administration of ivermectin drug was carried out annually between 1995 and 2001 in three villages that were endemic for onchocerciasis in the Lower Cross River Basin, Nigeria. The aim of this study was to evaluate the population dynamics (dispersion patterns, distribution, prevalence and intensity) of Onchocerca volvulus microfilariae in their human host after six years of ivermectin treatment. METHODS: A total of 1014 subjects from three rural areas in Etung Local Government Area of Cross River State, Nigeria were screened for skin microfilariae using standard parasitological method of diagnosis. RESULTS: Ivermectin drug intervention had significantly reduced the prevalence of skin microfilariae (PMF) from 69.3% pre-control to 39.3% and community microfilarial load (CMFL) from 7.11 to 2.31 microfilariae per skin snip. Males (45%) were significantly (p <0.05) more infected than females (34%). Both microfilarial prevalence and intensity increased with age. Pearson correlation test between intensity and age was not significant (r = 0.37; p >0.05). The correlation between age-dependent parasite prevalence and mean abundance was also not significant (r = 0.42; p >0.05). The degree of dispersion as measured by variance to mean ratio (VMR), coefficient of variation (CV) and exponent 'K' of the negative binomial model of distribution showed that the parasite aggregated, clumped and overdispersed in their human host. The relative index of potential infection of each age group showed that adults between the age of 21 and 50 yr accounted for 52.7% of microfilariae positive cases. INTERPRETATION & CONCLUSION: Aggregated and overdispersion of O. volvulus observed in this study showed that active transmission could still be going on, because the tendency of the vector, Simulium damnosum ingesting more microfilariae was high due to the aggregated and overdispersed nature of the parasite with its host.

Detection of Onchocerca volvulus (Nematoda: Onchocercidae) infection in vectors from Amazonian Brazil following mass Mectizan™ distribution

Detection of Onchocerca volvulus in Simulium populations is of primary importance in the assessment of the effectiveness of onchocerciasis control programs. In Brazil, the main focus of onchocerciasis is in the Amazon region, in a Yanomami reserve. The main onchocerciasis control strategy in Brazil is the semi-annually mass distribution of the microfilaricide ivermectin. In accordance with the control strategy for the disease, polymerase chain reaction (PCR) was applied in pools of simuliids from the area to detect the helminth infection in the vectors, as recommended by the Onchocerciasis Elimination Program for the Americas and the World Health Organization. Systematic sampling was performed monthly from September 1998 to October 1999, and a total of 4942 blackflies were collected from two sites (2576 from Balawaú and 2366 from Toototobi). The molecular methodology was found to be highly sensitive and specific for the detection of infected and/or infective blackflies in pools of 50 blackflies. The results from the material collected under field conditions showed that after the sixth cycle of distribution of ivermectin, the prevalence of infected blackflies with O. volvulus had decreased from 8.6 to 0.3 percent in Balawaú and from 4 to 0.1 percent in Toototobi.

Identification of entomopathogenic Bacillus isolated from Simulium (Diptera, Simuliidae) larvae and adults

Entomopathogenic bacteria isolated from Simulium larvae and adults from breeding sites in the states of Säo Paulo and Rio de Janeiro, Brazil, were identified as 18 strains of Bacillus thuringiensis and one of B. sphaericus. Most of these strains were serotyped according to their flagellar antigens. However, nine of the B. thuringiensis samples, could not be serotyped and were designated as "autoagglutinating"; they were also shown to be toxic in preliminary tests against Aedes aegypti larvae. Additionally, B. sphaericus was also shown to be toxic towards Culex quinquefasciatus larvae

Simuliid blackflies (Diptera: Simuliidae) and ceratopogonid midges (Diptera: Ceratopogonidae) as vectors of Mansonella ozzardi (Nematoda: Onchocercidae) in northern Argentina

Mansonella ozzardi, a relatively non pathogenic filarial parasite of man in Latin America, is transmitted by either ceratopogonid midges or simuliid blackflies. In the only known focus of the disease in north-western Argentina the vectors have never been incriminated. This study investigated the potential vectors of M. ozzardi in this area. The only anthropophilic species of these Diptera families biting man at the time of the investigation were Simulium exiguum, S. dinellii, Culicoides lahillei and C. paraensis. Using experimentally infected flies S. exiguum and both species of Culicoides allowed full development of microfilariae to the infective stage, with C. lahillei being a more competent host than S. exiguum. Based on these data, biting rates and natural infectivity rates it is probable that at the begininning of the wet season C. lahillei is the main vector of M. ozzardi and both C. paraensis and S. exiguum secondary vectors. Additionally, it was found that a single dose of ivermectin was ineffectual in eradicating M. ozzardi from infected individuals in this area

Effects of Polysispyrenia simulii (Microspora; Duboscqiidae) on development of the gonads of Simulium pertinax (Diptera; Simuliidae)

The effects of the infection caused by the microsporidium Polydispyrenia simulii in gonads of the simuliid Simulium pertinax were evaluated. This blackfly species is the main target of control programmes in southeastern Brazil. Infected and noninfected blackflies were reared from larval stage to adults using a laboratory rearing system. There was no significant difference between the oogenic development and dimensions of ovarian follicles of healthy females compared to those reared from infected larvae. Otherwise, there was a significant difference between the fecundity of healthy females and those reared from infected larvae. In males, there was an evident recuction of motility of spermatozoids of males reared from infected larvae. The results obtained suggest that the microsporidium P. simulii have an important effect on the natural population dynamics of S. pertinax.

Limnomermis subtropicalis n. sp. (Neumatoda: Mermithidae) a parasite of larvae of Simulium orbitale Lutz (Diptera: Simuliidae) in Argentina

Limnomermis subtropicalis n. sp. (Nematoda: Mermithidae) a parasite of larvae of Simulium orbitale Lutz (Diptera: Simuliidae) found in Argentina is described and illustrated. This species is characterized by having medium sized amphids, pocket-shaped, medium sized vagina, sculptured spicule, and by having 9 preanal, 7 postanal papillae in the ventral row, and 12 papillae in the lateral rows.

Cytological and isoenzyme analysis of the Bucay and Quevedo cytotypes of the onchocerciasis vector Simulium exiguum (Diptera: Simuliidae) in Ecuador

Four cytotypes of Simulium exiguum occur in Ecuador, where this morphospecies is the primary vector of onchocerciasis. In this paper, we give the first full description of the banding pattern of the larval polytene chromosomes of the Quevedo cytotypes differ from the chromosomal standard sequence (of the Cayapa cytotype) by the fixed inversions IIL-5 and IIL-6. The Quevedo cytotype additionally differs from the standard and Bucay cytotypes by processing a differentiated X chromosome, wich is indicated by the inversion IIS-A. As the degree of reproductive isolation between the Bucay and Quevedo cytotypes has not yet been estabilished, they must be regarded as intraspecific variants of the same species. In fact, isoenzyme characterizations showed that the Bucay and Quevedo cytotypes are differentiated only to the extent expected of incipient species or geographical populations. Moreover, the sibiling species status previously given to the Bucay cytotype needs be reassessed, there being inadequate analysis from areas in Ecuador where Bucay occurs in sympatry with the standard Cayapa cytotype. No isoenzyme electromorphs were discovered that identified all or mostadult females of any one (cytotype-pure) collection

Onchocerciasis in Ecuador: the situation in 1989

Details are given of the prevalence rates of onchocerciasis from the most recent surveys (1989) conducted in northern Ecuador. The disease has intensified and dispersed considerably due to migration of infected individuals and the presence of a highly efficient vector. Comparison of these data with those from two previous surveys carried out in 1982/83 and 1986 and correlated with entomological findings highly the danger of the formation of new foci of onchocerciasis in areas currently free of the disease. Recommendations are made for further entomological studies in areas either recently or likely to be affected by the disease where potential vectors are unknown or different to those registred in the Santiago focus. Invermectin treatment with local vector control in specific areas is advocated to reduce the disease to a low level of public health importance

Manifestaçöes oculares em doenças tropicais - II: oncocercose / Ocular manifestations in tropical diseases - II: onchocerciasis

Os autores descrevem suas experiências no estudo da oncocercose na Regiäo Amazônica. Relatam manifestaçöes clínicas e laboratoriais da doença detectadas por equipe multidisciplinar entre os índios Ianomani