Intensity Of Microfilaraemia Research Articles

Distribution of dirofilariasis in Omsk region

Background. Recently, in the Russian Federation, there has been a tendency to an increase in the number of registered cases of dirofilariasis among residents living in a temperate climate zone, including in Western Siberia. The species Dirofilaria repens and Dirofilaria immitis are of clinical importance for humans. Dirofilariae are characterized by migration into the subcutaneous tissue, mucous membranes, organs of vision, internal organs. In the Omsk region, there is an increase in cases of dirofilariasis, including among children.The aim. To assess endemicity of the territory of the Omsk region in relation to pathogens of dirofilariasis.Materials and methods. The maps of the epidemiological survey of persons infected with dirofilariae for the period 2013–2020 were analyzed, parasitological and molecular biological methods examined 1155 blood samples of dogs, 2488 samples female blood-sucking mosquitoes, 26 samples of dirofilaria helminths removed from residents of the Omsk region.Results. In 18 people, the infection was regarded as local, since the infected persons had not left the Omsk region for the previous three years. Local infections are reported annually. Infection of the final owners – dogs – with dirofilaria ranges from 0.6 to 4.8 % in different years. On average, the extensiveness of the invasion was 3.0 ± 0.6 %; and the intensity of microfilaremia was 1277.68 ± 395.87 specimens/ml of blood. On the territory of Omsk and the Omsk region, 11 species of mosquitoes belonging to the genus Aedes, Ochlerotatus, Culex, Anopheles, Coquillettidia were identified. The estimated individual infection of mosquitoes of different species ranged from 0.6 % (O. flavescens) to 9.8 % (An. messeae). The total infection of vectors was 3.4 %. All positive samples were found to contain DNA of D. repens.Conclusion. The territory of the Omsk region is endemic for pathogens of dirofilariasis, in particular, D. repens. Further studies are needed to study the prevalence and species diversity of pathogens of dirofilariasis in Western Siberia, to identify the most dangerous from an epidemiological point of view, species of vectors.

Familial Aggregation and Heritability of Wuchereria bancrofti Infection.

The familial recurrence risk of lymphatic filariasis (LF) is unknown. This case study aimed to evaluate the familial susceptibility to infection with Wuchereria bancrofti and to microfilaremia in a village of the Republic of Congo. The heritability and intrafamilial correlation coefficients were assessed for both W. bancrofti infection and microfilaremia by controlling for individual risk factors, environmental influence, and household effects. Pedigree charts were constructed for 829 individuals, including 143 individuals with a diagnosis of W. bancrofti circulating filarial antigens (CFAs) and 44 who also had microfilariae (MF). There was no intrafamilial correlation regarding CFA levels. However, the presence of MF (ρ = 0.45) and microfilarial density (ρ = 0.44) were significantly correlated among parent-offspring pairs. Heritability estimates for CFA positivity and intensity were 0.23 and 0.18, respectively. Heritability estimates were high for microfilarial positivity (h(2) = 0.74) and microfilarial density traits (h(2) = 0.81). Our study suggests that the acquisition of LF is mainly driven by environmental factors and habits and that genetic factors are moderately involved in the regulation of infection. By contrast, genetic factors play a major role in both the presence and intensity of microfilaremia.

Structure of the microfilarial reservoir ofLoa loain the human host and its implications for monitoring the programmes of Community-Directed Treatment with Ivermectin carried out in Africa

This paper describes the structure of the microfilarial reservoir of Loa loa in an endemic population of central Cameroon. The possible effects of age and sex on the prevalence and intensity of microfilaraemia have been explored. Logistic analysis showed that the prevalence of microfilaraemia increased significantly with age, reaching 60 % in the oldest males. This result suggests that the figure commonly reported, according to which only one third of the infected individuals were microfilaraemic, should be reconsidered; in addition, as part of surveys of loiasis, crude microfilaraemia prevalence values should be replaced by adjusted ones. The intensity of infection did not show any age-specific change. As a result, even if the oldest members of the male population are clearly the most at risk of developing post-ivermectin serious adverse reactions, especially Loa-encephalopathy, the other members of the population are not risk-free. Therefore, in those areas where the African Programme for Onchocerciasis Control is undertaking regular mass distributions of ivermectin for onchocerciasis control, and where loiasis is co-endemic, no subpopulation should be excluded from surveillance and monitoring during community directed treatments with ivermectin.

A community-based trial for the control of lymphatic filariasis and iodine deficiency using salt fortified with diethylcarbamazine and iodine.

To evaluate the effectiveness of salt fortified with diethylcarbamazine (DEC) and iodine for elimination of Bancroftian filariasis and iodine deficiency, all consenting residents of Miton, Haiti (n = 1,932) were given salt fortified with 0.25% diethylcarbamazine and 25 ppm of iodine for one year. Wuchereria bancrofti microfilaria prevalence and intensity, antigenemia, and urinary iodine were measured before and one year after salt distribution began. To measure the effect of DEC-fortified salt on adult worm motility, 15 microfilaria-positive men were examined by ultrasound of the scrotal area. Entomologic surveys were conducted to determine the proportion of W. bancrofti-infected Culex quinquefasciatus. After one year of treatment, the prevalence and intensity of microfilaremia were both reduced by more than 95%, while antigenemia levels were reduced by 60%. The motility of adult worms, as detected by ultrasound, was decreased, but not significantly, by DEC-fortified salt. The proportion of vector mosquitoes carrying infective stage larvae decreased significantly from 2.3% in the nine months before the intervention to 0.2% in the last three-month follow-up period. Iodine deficiency, which had been moderate to severe, was eliminated after one year of iodized salt consumption. The DEC-fortified salt was well accepted by the community and reduced microfilaremia and transmission to low levels in the absence of reported side effects. Based on these results, salt cofortified with DEC and iodine should be considered as a concurrent intervention for lymphatic filariasis and iodine deficiency elimination programs.

Randomised community-based trial of annual single-dose diethylcarbamazine with or without ivermectin against Wuchereria bancrofti infection in human beings and mosquitoes

WHO has targeted lymphatic filariasis for elimination. Studies of vector-parasite relations of Wuchereria bancrofti suggest that a reduction in the microfilarial reservoir by mass chemotherapy may interrupt transmission and thereby eliminate infection. However, no field data exist on the impact of chemotherapy alone on vector efficiency and transmission intensity of W bancrofti. We compared the impact of an annual community-wide single-dose treatment with diethylcarbamazine alone or with ivermectin on rate and intensity of microfilaraemia, and transmission intensity in an area of Papua New Guinea endemic for intense W bancrofti transmission. We carried out clinical and parasitological surveys in 14 communities in matched pairs. People aged 5 years or older in seven communities received randomly assigned diethylcarbamazine 6 mg/kg and people in the other seven communities received diethylcarbamazine 6 mg/kg plus ivermectin 400 micrograms/kg. We made physical examinations for hydroceles and leg oedema and investigated microfilarial densities by membrane filtration before and after treatment. We selected five communities for monthly entomological surveys between September, 1993, and September, 1995. Mosquitoes were collected in these communities by the all-night landing catch method and were individually dissected to identify rates of infection and infectiveness. 2219 (87.6%) of 2534 eligible people received treatment. Microfilarial rate and density had decreased 1 year after treatment in all 14 communities; this decrease was significantly higher in communities given combined therapy than in those given diethylcarbamazine alone (mean decreases 57.5% and 30.6%, respectively; p = 0.0013). Greater decreases were also seen in community-specific microfilarial intensity with combined therapy (mean reductions 91.1% and 69.8%, respectively; p = 0.0047). The rate of leg oedema was not altered, but the frequency of advanced hydroceles decreased by 47% with combined therapy and 56% with diethylcarbamazine alone. 26,641 Anopheles punctulatus mosquitoes were caught during 499 person-nights of landing catches. Exposure to infective third-stage larvae decreased in all monitored five communities. Annual transmission potential decreased by between 75.7% and 98.8% in combined-therapy communities and between 75.6% and 79.4% in communities given diethylcarbamazine alone. Transmission was almost interrupted in two communities treated with combined therapy. Annual single-dose community-wide treatment with diethylcarbamazine alone or with ivermectin is effective for the control of lymphatic filariasis in highly endemic areas, but combination therapy brings about greater decreases in rates and intensity of microfilaraemia.

Antifilarial IgG4 Antibodies In Children From Filaria-Endemic Areas Correlate With Duration Of Infection And Are Dissociated From Antifilarial IgE Antibodies

To investigate the relationship of antifilarial IgG4 and IgE to the intensity of transmission and duration of filarial infections in endemic populations, antifilarial antibody levels in children residing in a village in Papua New Guinea where transmission of Wuchereria bancrofti was reduced by repeated insecticide spraying were compared with levels in residents of three nearby villages where no control measures had been used. Antifilarial IgG4 levels were significantly lower in children from the sprayed village than in children or adults in nonsprayed villages (P < .01) and correlated with age (P < .05) and intensity of microfilaremia (P < .01). In contrast, antifilarial IgE was elevated to similar levels in children and adults from both villages. Antifilarial IgG4 (and not IgE) levels in endemic populations appear to be directly related to the duration of infection or to the cumulative exposure to infective vectors.

Immune response to Acanthocheilonema viteae infection in multimammate rats (Mastomys natalensis)

The multimammate rat Mastomys natalensis, when infected with the filarial parasite Acanthocheilonema viteae, develops amicrofilaraemia. Worm recovery and the duration and intensity of microfilaraemia were analysed and related to the humoral and cellular immune responses of the host by using an antibody-dependent cell-mediated cytotoxicity (ADCC) assay towards microfilariae (Mf). Mf were detected in the peripheral blood at 7 weeks post-infection (p.i.), reaching maximum levels by 20 weeks p.i., and then gradually decreasing to undetectable levels during the next 36 weeks. The cytotoxic antibodies appeared around 15-18 weeks p.i., and the serum at 36 weeks p.i. induced 70% cytotoxicity to the Mf in vitro in the presence of host cells. The IgM fraction of the immune serum from amicrofilaraemic Mastomys promoted ADCC to Mf both in vitro and in vivo. Macrophages were more potent in inducing cytotoxic effect than eosinophils and neutrophils. Platelets were ineffective in killing the Mf in the presence of immune serum. IgM antibody cleared the circulating Mf from the blood when given passively to infected Mastomys. The average recovery of adult worms was about 20% of the inoculated larvae. No live females could be recovered 56 weeks p.i. Thus protective immune responses built up over an extended period of time are elicited against the Mf and perhaps even to adults in Mastomys infected with A. viteae.

Bancroftian filariasis in Pondicherry, south India: 2. Epidemiological evaluation of the effect of vector control.

This article examines the evaluation of a bancroftian filariasis control programme undertaken in Pondicherry from 1981-5. Integrated vector management was applied in one half of the town, and routine operations under the national programme (larviciding and chemotherapy) continued in the comparison area. The programme was evaluated by monitoring relative change in the epidemiological statistics of both populations. The results indicate that there was significant reduction in prevalence of microfilaraemia in juveniles in the controlled area. An apparent reduction in intensity of microfilaraemia was also observed but this was a consequence of the reduction in prevalence, since the density of microfilariae remained unchanged. The results suggest that primary constraints on the epidemiological evaluation of the vector control of filarasis are the longevity and the population characteristics of the parasite.

Identification of Phosphorylcholine Epitope-Containing Antigens in Brugia Malayi and Relation of Serum Epitope Levels to Infection Status of Jirds with Brugian Filariasis

The Gib 13 monoclonal antibody was raised against eggs of Onchocerca gibsoni and subsequently found to react with a phosphorylcholine epitope designated as the T15 idiotype. Since an immunoradiometric assay based on the Gib 13 monoclonal antibody holds promise for serodiagnosis of filariasis, the goals of the current study were to evaluate phosphorylcholine epitope production and release by various parasite stages and to assess changes in serum epitope levels during different phases of Brugia malayi infection in jirds. Extracts of B. malayi adult male worms, female worms, and microfilariae contained Gib 13 monoclonal antibody-reactive antigens of Mr 25-30,000, 57-90,000, and approximately equal to 200,000. Adult female worms secreted ten-fold more epitope than microfilariae on a weight basis. Phosphorylcholine-containing antigens were localized in female and male worms, respectively, in egg-bearing regions and the intestines. Assessment of the relationship between serum levels of Gib 13 antibody-binding epitope and parasitologic status of B. malayi-infected jirds showed that the immunoradiometric assay distinguishes patent infected from uninfected control animals, detects a significant rise in epitope level during the prepatent phase of infection, and is unaffected by diethylcarbamazine-induced reduction in the intensity of microfilaremia. There was a direct positive correlation between serum epitope level and female adult worm load. Quantification of serum phosphorylcholine epitope of the T15 idiotype may be useful as an indirect measure of parasite burden in humans with lymphatic filariasis that is independent of microfilaremia.

Natural Transition Of Endemicity Of Malayan Flariasis In Inland Korea: Pattern Of Change In Microfilaria Rate Among Inhabitants Of Yongpung (Former Yongju) Area During The Period Of The Last Seven Years

With a purpose to find out natural transition of endemicity of Malayan filariasis in inland Korea, a survey was conducted in June 1980 in Isan-Myeon of Yongpung-Gun (former Yongju-Gun) where an epidemiological investigation had been carried out in 1973 without any control activities such as chemotherapy. Five sample villages were surveyed for microfilaremia by 20 microliter night blood examination among inhabitants and the results of the surveys conducted in 1973 and 1980 were compared to determine natural transition of the endemicity of malayan filariasis during the period of the last 7 years. 1. The current microfilaria rate among inhabitants in the 5 villages was 2.2 % on the average (male: 1.6 %, female: 2.8 %) from 370 persons examined. By village, the rates were 5.9 % (number of persons examined: 34) in Baranggol, 0 % (30) in Guitonggl, 4.2 % (72) in Alseonggol, 0 %(65) in Jangjagol and 1.8 % (169) in Saehae. 2. Extremely low microfilaria rate was noted in young age groups. By age group, no positive case was found in those age groups below 30~39 years except 10~14 age group in which 2 positives (4.4 %) were found. Two positives each were found in the respective age groups of 40~49(3.2 %), 50~59 (4.4 %) and over 60 (3.4 %). 3. In evaluation of the natural transition of the endemicity during the period of the last 7 years, the microfilaria rate turned out from 13.1 % in 1973 to 2.2 % in 1980. The difference in the microfilaria rate was 10.9 % and the natural reduction rate per year was 1.6 % on the average. 4. From the examination of 35 cases which had revealed microfilaremia 7 years ago, 85.7 %(30) of them were found to have converted to microfilaria negatives. On the other hand, from the 151 cases which had revealed no microfilaria in 1973, only 0.7 % (1) of them was found to have converted to microfilaria positive. 5. In the intensity of microfilaremia, the number of microfilaria/20 microliter blood per positive case was 11.0 in 1973 and 9.1 in 1980. The number of microfilaria/20 microliter per examinee was 1.4 in 1973 and 0.2 in 1980, thus reduced to 1/7 during the period of the 7 years. 6. The retarding endemicity of malayan filariasis in inland Korea was considered to be resulted in by the gradual increase of environmental factors in relation to ecology of vector mosquitoes, which adversely affect to the transmission of malayan filariasis. Followings are suggested to be the factors which control the transmission of the malayan filariasis in this area: 1) Inhabitants are the only natural final host of Brugia malayi infection in this area, 2) Gradual elevation of living standards of the inhabitants, 3) Gradual awakening of consciousness and behavior among inhabitants to protect themselves from mosquito biting using such as mosquito nets and insecticide sprays, 4) Preference of animal bait of vector mosquitoes, Anopheles sinensis, 5) Increase in number of domestic animals and fowls being raised in the village areas which play a major part of blood donors to vector mosquitoes, and 6) Relatively short (3~4 months) period of mosquito season in a year.

Host-parasite relations in cotton rat filariasis. III

The quantitative transmission of Litomosoides carinii by Liponyssus bacoti to un-irradiated and irradiated hamsters and mice is described. Both young and adult, un-irradiated and irradiated hamsters were highly susceptible to L. carinii but mice (un-irradiated or irradiated) were poor hosts. All hamsters (18 un-irradiated and seven irradiated) became infected. Seven out of nine mice in an un-irradiated series became infected. There was apparently 'age resistance' or 'young susceptibility' in the hamsters. The susceptibility of young hamsters appeared similar to that of new-born Carworth white rats and cotton rats. The pattern of infection in un-irradiated and irradiated hamsters was similar. Results from irradiated animals were insufficient to draw any clear conclusions on the effect of irradiation to susceptibility to infection with L. carinii. X-irradiation apparently did not affect the innate susceptibility cr resistance of hamsters and mice to worms. The duration and intensity of microfilaraemia was apparently higher in irradiated hamsters.