Microfilarial Density Research Articles

Efficacy of Chloroquine, Ivermectin and Artemether on Onchocerca Gutturosa in Zebu calves in Sudan.

Skin microfilarial (mff) densities, adult worm recovery and embryogenesis in gravid female worms were used to evaluate the efficacy of Chloroquine, Ivermectin and Artemether against Onchocerca gutturosa in three groups of five natural y infected zebu calves 2-3 years old. Chloroquine and Artemether were highly effective against both dermal mff and adult worms. Skin mff densities was declined rapidly within two- to three- days of injection and complete clearance occurred thereafter for the fol ow up period (4 months). Four months after the last dose of each drug, the animals were slaughtered and the adult worms examined. Al three drugs showed significant mortality rates i.e. 27%- 32% among adult female worms (P

Individual host factors associated with Onchocerca volvulus microfilarial densities 15, 80 and 180 days after a first dose of ivermectin

Reduction in Onchocerca volvulus skin microfilarial densities after treatment with ivermectin shows wide between-host variation. Data from two separate studies conducted in Cameroon on onchocerciasis patients treated for the first time with ivermectin were analyzed to identify host factors associated with microfilarial density at different time-points after treatment. In one site (Nkam valley), the dataset included 103 adult males for whom age, number of palpable onchocercal nodules and microfilarial densities on D0 (pre-treatment), D15, D80 and D180 were available. In the other site (Vina valley), analyses were conducted on 965 individuals of both sexes aged 5 years and over; in this dataset, available information included age, gender, exact dose of ivermectin received, onchocerciasis endemicity level in the village of residence and microfilarial densities on D0 and D180. Negative binomial regression models of microfilarial density at the different intervals post-treatment were fitted, using maximum likelihood, with the available independent variables. Gender and age were found to be associated with microfilarial density on D180. The initial microfilarial density influenced post-treatment densities at all the time-points. All other things being equal, microfilarial densities on D180 were higher in individuals harbouring a higher number of nodules or living in communities with high endemicity levels. This study demonstrates that O. volvulus microfilarial density measured after a first treatment with ivermectin, and thus probably the rate of skin repopulation by microfilariae (mf) varies according to several host factors.Should such factors also influence ivermectin efficacy after repeated treatment, then they should be taken into account to determine whether sub-optimal responses to treatment reported from various areas in Africa are actually due to parasite-related factors, particularly to the emergence of resistant populations.

The role ofOnchocerca volvulusin the development of epilepsy in a rural area of Tanzania

Several reports indicate high prevalences of both onchocerciasis and epilepsy in some regions of Africa. This raises the question of whether these diseases are associated. We therefore investigated people with epilepsy and/or onchocerciasis living in an area in Tanzania endemic for Onchocerca volvulus (O. volvulus). We collected clinical information, skin snips, and blood from 300 individuals, and cerebrospinal fluid (CSF) from 197. Participants were allocated to 4 groups consisting of people with epilepsy and onchocerciasis (n=135), those with either epilepsy (n=61) or onchocerciasis only (n=35), and healthy individuals (n=69). Samples were evaluated for microfilaria, IgG4 antibodies against O. volvulus, O. volvulus antibody index (CSF/serum), and CSF routine parameters. Polymerase chain reaction (PCR) was performed on skin snips and CSF. No difference was found in microfilarial density between participants with and without epilepsy (P=0.498). The antibody index was raised in 2 participants. CSF PCR was negative in all samples tested. Our results do not give evidence of a relationship between O. volvulus and epilepsy. Despite the fact that 2 participants had raised antibody index, the existence of cerebral onchocerciasis caused by migration of microfilariae into the CSF appears unlikely. However, to date unexplored reactions to the infestation with O. volvulus causing epilepsy cannot be excluded.

Bancroftian filariasis in Kwale district, Kenya.

To determine the prevalence of Wuchereria bancrofti infection in an area designated for filariasis control trial. A cross-sectional survey. Three villages in Kinango location, Kwale district, Coast Province, Kenya. Oral informed consent to participate was obtained from adults and parents or guardians of children below fifteen years of age. Microfilaraemia prevalences, microfilarial densities and clinical manifestations. The overall prevalence of microfilaraemia in the population was 16.4%. The prevalence of microfilaraemia was age-dependent and the overall microfilarial density (MFD) was 69.4 mf/ml (geometric mean) and significantly higher in males (95.8 mf/ml) than in females (48.6 mf/ml) (p < 0.05). The prevalence of clinical signs of infection was also age-dependent with elephantiasis being significantly higher in females (2.3%) than in males (0.9%) (p < 0.05). Among the males, the major clinical manifestation was hydrocele (10.4%). These findings show high prevalence of bancroftian filariasis in Kwale district and warrant similar studies followed by implementation of intervention measures to reduce transmission in all areas of endemicity in the Coast Province.

Onchocerciasis in Gilgel Ghibe River Valley southwest Ethiopia.

To determine the prevalence of onchocerciasis and the entomological transmission indices such as the parous rate and annual transmission potential (ATP). Gilgel Ghibe village, Gilgel Ghibe River Valley Southwest Ethiopia between April 1994 and March 1995. Two hundred twenty eight subjects of the total 400 population in Gilgel Ghibe village were subjected to parasitological and clinical examinations. Two skin snips per person were taken and examined for microfilariae of Onchocerca volvulus. Fly collections were done from dawn to dusk from human baits seated in pairs at four representative sites at the river bank and away from the river bank. Flies were dissected for parity and infections with O. volvulus larvae. Among the 228 people examined, the prevalence of the disease was low (17%), being higher in males (19%) than in females (14%). The geometric mean of microfilarial density was 11.1 (range, 1-132) mf per skin snip. Itching followed by pigmentary changes were the most common clinical signs and symptoms. The predominant anthropophilic blackfly species was Simulium (Edwardsellum) damnosum s.l. The annual parous rate and ATP were 74.7% and 1669.5, respectively, being higher at the river bank than at sites further away suggesting a greater risk of infection by the river side. The low prevalence of onchocerciasis in Gilgel Ghibe area vis-a-vis the high ATP level could be due to the possible presence of bovine onchocerciasis in the area. Further studies employing molecular techniques are thus required to identify O. volvulus from other filariae in flies.

In vitro and in vivo antifilarial potential of marine sponge, Haliclona exigua (Kirkpatrick), against human lymphatic filarial parasite Brugia malayi

The present study reports on the antifilarial activity of a marine sponge Haliclona exigua (phylum Porifera). The crude methanol extract and n-butanol-soluble fraction killed adult Brugia malayi at 31.25-microg/ml concentration (both in motility and 3-(4,5 dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide assay) while the chloroform fraction was lethal at a lower concentration of 15.6 microg/ml. The activity could be located in a single molecule araguspongin C which brought about mortality of worm at 15.6 microg/ml. In vivo evaluation of the crude extract (5 x 500 mg/kg, orally) and the chloroform fraction (5 x 250 mg/kg, orally) in B. malayi-infected rodent host, Mastomys coucha, did not show any significant microfilaricidal actions; however, microfilarial densities in both the treated groups were significantly much lower than those of untreated group in contrast to standard filaricide diethylcarbamazine which exerted 79% microfilaricidal action on day 8 of treatment. Both these extracts also demonstrated adulticidal (macrofilaricidal) activity which was more pronounced in the chloroform fraction (50.2%). In addition, there was moderate adverse effect on the reproductive potential of female worms (crude extract 46.5%; chloroform 58.6%). The findings suggest that the marine sponge H. exigua possesses adulticidal and embryostatic action against human lymphatic filarial parasite B. malayi in experimental rodent model and this activity could be attributed to the presence of araguspongin C.

Impact of 3 years ivermectin treatment on onchocerciasis in Yanomami communities in the Brazilian Amazon

In the current study, it was assessed, for the first time, the effect of ivermectin treatment administered twice a year on the prevalence and morbidity of onchocerciasis in the hyperendemic Yanomami communities of the Roraima State (Brazil). Physical and parasitological examinations were carried out every 6 months until six drug rounds of treatment were completed. The coverage during the six rounds of ivermectin treatment ranged from 89% to 92% of the eligible Yanomami population. Overall, comparison of results at pre-treatment with results after six rounds of treatment, the prevalence of infection had declined from 87% to 42% ( P < 0.0001, CI 95% = 0.05–0.22); the community microfilarial load (CMFL) fell from 1.17 to 0.53 Mf/mg of skin; and the crude intensity of infection (MFL-Total) decreased from 18.95 to 1.96 Mf/mg of skin during the same period ( P < 0.0001, for both microfilarial loads). Although no significant difference was observed between microfilarial densities in skin snips from iliac crest and scapula after the 6th round of ivermectin treatment it was observed that the prevalence of positive skin snips was significantly higher when skin snips were taken from iliac crest (42%) than from scapula (8%) ( P = 0.001, CI 95% = 3.41–22.67). After six rounds of ivermectin treatments, no significant differences were observed in the prevalences of palpable nodules and of onchodermatitis in relation to pre-treatment prevalences, from 45% to 41% and from 17% to 20% ( P > 0.05, for both). These findings suggest that mass population treatment should continue without interruption and achieve higher levels of drug coverage in order to alleviate disease manifestations and interrupt infection transmission to hasten the elimination of onchocerciasis in Yanomami communities. In addition, the sensitivity of iliac crest snips for parasitological assessment in epidemiological surveillance of Yanomami communities may increase the acceptance of the population in biopsy sampling and seems to be a good choice for assessing the success of control programs.

Ultrastructural analysis of microfilariae of Wuchereria bancrofti obtained from persistent carriers after repeated courses of diethylcarbamazine

Single dose of diethylcarbamazine (DEC) used in control programs is effective in breaking the transmission of filariasis. In order to investigate the effect of aggressive therapy on Wuchereria bancrofti ( Wb) microfilariae, DEC was given to 29 patients who were positive for the circulating filarial antigen (CFA) assay but did not have clinical manifestations of filariasis, at 6 mg/kg/day for 12 days and again six months later using the same dosing regimen. For each patient, microfilarial density and serum CFA were followed up for two years. Ultrastructural analyses on Wb microfilariae obtained after repeated treatment with DEC were also performed. Microfilaremia and antigenemia decreased significantly after 12 months but returned to the initial levels after 24 months. This could indicate, as shown by other authors, that aggressive repeated therapy with DEC alone is ineffective in eradicating adult W. bancrofti, particularly in infected but asymptomatic individuals. The objective of the present study was to analyze the microfilaremic and antigenemic behavior and ultrastructural changes caused by different DEC concentrations in vitro in Wb microfilariae obtained from individuals who were sensitive and refractory to treatment. After in vitro treatment of the microfilariae using 5 and 10 μg/ml of DEC for 1 h, ultrastructural analysis revealed low levels of cell damage compared with embryos obtained from individuals from a different area who had never received DEC treatment before. The results obtained suggest that microfilariae from patients who receive repeated aggressive therapy are less sensitive to DEC in vitro.

An epidemiological study of filariasis in a village of district Datia, MP

Background:District Datia has been known to be endemic for filariasis. A number of cases have been reported in recent past. The present study was an epidemiological investigation carried out in village Barganya, Datia in the month of Sept 2004.Aims and Objectives:The objectives of this study were to confirm the epidemic in village Barganya and to study the causes of the present epidemic.Materials and Methods:The study was a cross sectional study carried out through house to house survey, covering a population of 1512.Result:A total of 78 clinically confirmed cases were reported. The study calculated a microfilarial rate of 6.9% and 1.65% in males and females respectively. The microfilarial density among confirmed cases ranged from 3.1 to 10.6 per 20 cmm.Conclusion:The study concluded that majority of the cases were males who worked in open field and there was a lack of proper management of these cases at village level.

Successful control of lymphatic filariasis in the Republic of Korea.

A successful experience of lymphatic filariasis control in the Republic of Korea is briefly reviewed. Filariasis in the Republic of Korea was exclusively caused by infection with Brugia malayi. Over the past several decades from the 1950s to 2006, many investigators exerted their efforts to detection, treatment, and follow-up of filariasis patients in endemic areas, and to control filariasis. Mass, combined with selective, treatments with diethylcarbamazine to microfilaria positive persons had been made them free from microfilaremia and contributed to significant decrease of the microfilarial density in previously endemic areas. Significant decrease of microfilaria positive cases in an area influenced eventually to the endemicity of filariasis in the relevant locality. Together with remarkable economic growth followed by improvement of environmental and personal hygiene and living standards, the factors stated above have contributed to blocking the transmission cycle of B. malayi and led to disappearance of this mosquito-borne ancient disease in the Republic of Korea.

Prevalence of Onchocerciasis and IgG3 Response among the population of Poli (North Cameroon)

Poli is one of the areas with high endemicity of onchocerciasis in Cameroon. Invermectin distribution campaign started there since 1993 but there has been no evaluation of the contribution of this measure to the decrease of the prevalence of the disease in the covered area. This study sort to determine the prevalence of onchocerciasis the microfilarial load and IgG3 levels of randomly chosen indigenous (112) who spent most of their lifetime in the Poli area. All persons retained for examination had either never taken ivermectin or had their last dose of ivermectin more than six months before the starting of the present study. The overall prevalence of human onchocerciasis in the eight villages studied was 65.18%. The prevalence was higher (68%) in males than females (59.45%). The microfilarial (mf) density was also higher in the male population (1.48mf/mg of skin) than the females (1.34mf/mg of skin). The prevalence of onchocerciasis for the four age groups: 5—20 years. 21—30 years. 31—50 years. >50 years 58.33%, 53.57%, 75.00%, 70.83% respectively while the microfilarial density for these same age groups (1.15mf/mg of skin, 1.46mf/mg of skin, 1.68mf/mg of skin respectively. IgG3 response was higher in females than males and globally, IgG3 levels increased with age in onchocerciasis patients. Sex and age significantly influence the prevalence (P 0.05). It is evident from this study that after close to a decade of onchocerciasis control in Poli, the disease is still highly endemic there. Health personal in Poli, high authorities of Cameroon Ministry of Public Health and the W.H.O are therefore alerted to visualise new strategies to reinforce control measures in view of the eradication of ‘‘river blindness’’ in Poli using the present epidemiological picture.

Effect of single to triple dose DEC on microfilaremics up to 5 years

A 5-year study was conducted with 200 selected microfilaremic subjects bearing Mean microfilarial density (MMD) of 11.6 from 16 small foothill villages around Susunia Hill, Bankura, West Bengal during June 2001 to May 2002. All of them were treated with a single dose (6 mg/kg body weight) to triple dose diethylcarbamazine (DEC). On day 180, 365, 730, 1,095, 1,460, and 1,825, recurrence of microfilaremia were 0.0%, 6.0%, 15.5% (6 + 9.5), 27% (15.5 + 11.5), 42% (27 + 15), and 49% (42 + 7), respectively, and corresponding MMD were 0.0, 1.2, 1.4, 2.7, 6.2, and 7.8, respectively. Culex quinquefasciatus was incriminated as the vector and their infection and infectivity rates reduced to 4.2% and 0.81% from the initial values of 6.40% and 1.33%, respectively, after DEC treatment to selected mff carriers. Single-dose DEC treatment was found effective for reduction of microfilaremia and MMD but it was not always sufficient to eliminate all the microfilariae, especially when MMD was high (>40). For microfilaremics with high MMD, a single course (6 mg/kg body weight for 3 days) DEC treatment may be safe for the first instance.

Dirofilaria immitis infection in dogs: unusually located and unusual findings

Clinical, blood, serum biochemistry, and parasitological assessments were performed on four hospitalized dogs, not in good general condition, in a study carried out to determine the prevalence of general parasitic infections. Hematological and biochemical parameters and electrocardiographic recording of the animals were determined during the general clinical examinations. Four dogs were indicated to have been infected with Dirofilaria immitis by using modified Knott's method, and the microfilarial density was determined. Mild to moderate anemia and decrease in sedimentation velocity were established in dogs. Differences in other hematological and biochemical values between the dogs were determined. Right axis deviation was determined in a dog. D. immitis was encountered in the right ventricle, bronchus, and the pericardial sac at the end of the necropsy. On the other hand, in the histopathological examinations, pulmonary adenocarcinoma deriving from bronchial epithelium was identified in a dog, and microfilaria was encountered in bronchial and bronchiolar lumens, interstitium of the lungs, and bile ducts. D. immitis has not been considered in the diagnosis of dogs with pneumonia and tumors. The requirement of parasitological examination with respect to D. immitis in the diagnosis of dogs with tumor or pneumonia has been considered vital.

Lymphatic filariasis in the coastal areas of Digha, West Bengal, India

The state of West Bengal, India, has a long coastline with the Bay of Bengal. No information exists regarding filarial epidemiology and its vector in these coastal areas. The present study was designed to assess the epidemiology of lymphatic filariasis and the role of available mosquitoes as its vector in eight coastal villages around Digha, West Bengal. Night blood samples of 4016 individuals were collected and each of them was examined clinically for any manifestations of the disease. Overall, microfilaria rate, mean microfilarial density and disease rate were 9.06%, 8.63% and 7.72%, respectively. The causative parasite was identified as Wuchereria bancrofti and Culex quinquefasciatus was incriminated as the vector responsible. Vector infection and infectivity rates were assessed to be 12.5% and 0.73%, respectively. The human blood index of human-house-frequenting vector population was 70%. Vector density, vector infection, infectivity rates and human blood index were higher in the rainy season in the study area. Overall, the filarial situation was bad and, as a measure, single-dose diethylcarbamazine citrate (6 mg/kg body weight) treatment was given to all the microfilariaemic patients. Night blood samples of the treated individuals were tested for microfilariae on days 10 and 365, which revealed interesting results.

Prevalence of lymphatic complications due to onchocerciasis infection in Imo State, Nigeria

The study was conducted to determine the prevalence of lymphatic complications due to onchocerciasis infection in 38 endemic rural communities in the Imo River Basin, Nigeria. Using standard parasitological and clinical methods of diagnosis, 7,144 consenting individuals aged 5 years and above were examined for Onchocerca volvulus microfilaria and clinical lymphatic symptoms of onchocerciasis. Of the 7,144 individuals, examined, 1,646 (23.0%) were positive for O. volvulus microfilariae, while 1,045 (14.6%) had various degrees of lymphatic complications. The prevalence of lymphatic complications were lymphadenopathy (7.9%), hanging groin (3.2%) and inguinal hernia (3.5%). Subjects 30 years and above had the highest microfilarial densities which coincided with higher prevalences of these lesions suggesting their chronicity. Sex-prevalence showed an insignificant borderline difference, 17.3% in males and 14.3% in females (p > 0.05). Lymphadenopathy and hanging groin were strongly associated with microfilarial density (r = 0.54; p

Randomized, controlled, double-blind trial with ivermectin on Loa loa microfilaraemia: efficacy of a low dose (∼25μg/kg) versus current standard dose (150μg/kg)

Neurological serious adverse events (SAEs) following ivermectin treatment may occur in individuals harbouring high Loa loa microfilarial densities and are of major concern in the context of mass ivermectin distributions organized in Africa for onchocerciasis and lymphatic filariasis control. As those SAEs are induced by the rapid and massive microfilaricidal effect of a standard dose of ivermectin (150 microg/kg), we performed a randomized, controlled, double-blind trial to determine whether ivermectin given as: (a) a single low dose of 1.5mg (i.e. 25 microg/kg for a 60 kg person); or (b) two doses of 1.5mg given at a 2 week interval leads to a more progressive decrease in Loa microfilarial loads compared with the standard dosage. A low dose of ivermectin brought about a significantly smaller decrease in Loa microfilaraemia than the standard dose. However, this decrease was not sufficiently different from that obtained after the standard dose to be acceptable to public health programmes, which require a wide safety margin. A second low dose of ivermectin given 15 days after the first dose did not lead to a further decrease in Loa microfilaraemia. Lastly, the variability in the response observed in the group treated with 25 microg/kg suggests that even lower doses would have no effect on a significant number of patients. Ivermectin given at a low dose (<or=25 microg/kg) is probably not adequate to prevent the occurrence of post-treatment neurological SAEs.

Hanging groin and persistent pruritus in a patient from Burkina Faso

Onchocerciasis is a filarial disease caused by Onchocerca volvuvus which can lead to skin, bladder or ocular signs. The authors report a 6-month history of generalized pruritus and two bilateral and symmetric masses in inguinal areas in a 57-year-old black woman. Skin snips and a biopsy of a subcutaneous nodule were diagnosed as onchocerciasis with hanging groin and the patient was treated with ivermectin with a dramatic improvement. If pruritus is the most constant symptom of onchocerciasis, hanging groin is usually observed only in hyperendemic areas in association with high microfilarial density. As no protective immune response is acquired after onchocerciasis, it is recommended that observation is maintained in communities where blindness is less common but where skin manifestations remain prevalent. There is a risk of misdiagnosing onchocerciasis owing to its long incubation period and its unfamiliarity to physicians in nonendemic areas.

Laboratory investigation of the infection rate of &lt;i&gt;Anopheles gambiae&lt;/i&gt; and &lt;i&gt;Anopheles funestus&lt;/i&gt; in the transmission of &lt;i&gt;Wuchereria bancrofti&lt;/i&gt;

Laboratory-bred Anopheles gambiae and An. Funestus , mosquito vectors of lymphatic filariasis in parts of Africa, were fed on a Wuchereria bancrofti carriers of known microfilarial density after four days of adult life. Of the 180 mosquioes used for the experimens only 56(62.2%) of An. Funestus and 49(54.4%) of the An. gambiae actually fed on he carriers' blood. After 14 days post-infection period, 9(16.7%) harboured pre-infective L2 larval stages while 34(60.7%) of the engorged An. Funestus harboured infective L3 larval stages of W. bancrofti with mean infective L3 larval stage/mosquito of 3.06 ₫ 2.13 (mean ₫ S.E). Similarly at the post-infective period, 36(73.5) of the engorged An. Gambiae harboured L3 infective larval stages of W. bancrofti with a mean L3 larval stage/mosquito of 3.5 ₫2.26 (mean ₫ S.E). Only 4.1% of the mosquitoes harboured L2 pre-infective stages. Results showed that both species of Anopheles were susceptible to the local strain of W. bancrofti microfilariae as there was no significant difference in infection rates attributable to Anopheles species. The Nigerian Journal of Parasitology Vol. 24 2003: 143-148

Onchocerciasis in Imo State, Nigeria; Clinical and epidemiological studies of anterior segment lesions

A clinical and epidemiological assessment of Ocular Onchocerciasis with respect to Anterior Segment Lesions (ASLs) was carried out in 7348 consenting persons living in 38 rural communities in the Imo River Basin of Nigeria between March 1999 and September 2000. the results showed that 40.0% (2934/7348) of the subjects had one form of ASLs. Blurring of vision (10.1%) was the most prevalent lesion followed by anterior uveitis (8.5%) while the least was blindness (with no light perception) (0.2%). ASLs were absent in the 0-9 year group but increased in relation to microfilarial density (mfd) in the older age groups. Sex-prevalence of ASLs showed insignificant borderline differences in all case (p>0.038). Blindness was weakly associated with mfd (r=0.32;p

Studies on the microfilarial density and annual transmission potential of &lt;i&gt;Mansonella perstans&lt;/i&gt; by &lt;i&gt;Culicoides&lt;/i&gt; species in selected communities of Ogoniland, Rivers State, Nigeria

Studies on the microfilarial density and annual transmission potential of &lt;i&gt;Mansonella perstans&lt;/i&gt; by &lt;i&gt;Culicoides&lt;/i&gt; species in selected communities of Ogoniland, Rivers State, Nigeria