Microfilaria malayi in uveitis: case report.
A case of uveitis with microfilariae in the anterior chamber is reported. The organism was recovered from the aqueous and identified as Brugia malayi.
Anterior Chamber↗
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Immunologic response in onchocerciasis: relations to microfilaria density in the skin biopsy and to some frequent symptoms.
During physical and immunologic investigations on onchocerciasis in 1,298 persons in the Republic of Liberia, the following results were obtained. There is a significant correlation between immune response and Onchocerca volvulus infection detected by a microfilaria-positive skin biopsy. On the other hand, the immune response is not influenced by the number of parasites in the skin, and there is no correlation of the immune response with Onchocerca nodules and with pruritus. There is a high proportion of serologically false-positive and false-negative results, and thus a diagnosis cannot be made simply by establishing evidence for antibodies in one person.
Adolescent↗
Experimental studies on the transmission of Onchocerca volvulus by its vector in the Sanaga valley (Cameroon): Simulium squamosum B. Intake of microfilariae and their migration to the haemocoel of the vector.
As large-scale ivermectin distribution is becoming the mainstay of onchocerciasis control in Africa, the issue of its impact on local transmission is increasing in importance. The vector competence of Simulium squamosum B in the severe focus of the Sanaga valley, Cameroon, was therefore investigated, by feeding 1320 flies on 14 carriers of Onchocerca volvulus microfilariae (mff). The results enabled the relationships between skin microfilarial load, microfilarial intake by the flies, the proportion and mean number of ingested mff that succeed in reaching the fly's haemocoel, and the frequency distribution of the ingested mff to be described, as functions of time post-engorgement (p.e.) and parasite density (while taking account of possible measurement error in the predictor variable). The proportion of flies with haemocoelic mff and the mean number of mff/fly increased up to 3 h p.e. The proportion of flies with ingested mff was non-linearly related to mean intake, via the negative-binomial distribution, with the overdispersion parameter k best described as an increasing (power) function of the mean. Approximately one in every three ingested mff escaped imprisonment by the peritrophic matrix, irrespective of the skin microfilarial load or the intake of mff. The relationship between successful and input mff is nearly linear (indicating proportionality) in S. squamosum B. These results are compared with those from O. volvulus-S. damnosum s.l. combinations in other West African foci.
Adolescent↗
Rapid assessment of the geographical distribution of Mansonella perstans infections in Uganda, by screening schoolchildren for microfilariae.
The geographical distribution of Mansonella perstans infections in Uganda was assessed by day-time examination of school-aged children for microfilariae. Overall, 12,207 children from 76 sites representing the various topographical and ecological zones in the country were examined. Children with M. perstans microfilaraemia were detected at 47 (61.8%) of the study sites, with prevalences ranging from 0.4% to 72.8%. A broad, east-west-oriented belt of high endemicity was identified, stretching across the central part of the country from the southern end of Lake Albert to the north-western shores of Lake Victoria. To the north and south of this belt prevalences generally decreased, although high-prevalence foci were also identified in the far north-western and south-eastern corners of the country. Geostatistical interpolation was used to create a map showing the geographical distribution of M. perstans prevalences in Uganda (by ordinary kriging), and to assess the population exposed to M. perstans transmission. Estimates based on population data from 2002 indicated that 20.4 million people (82.6% of the national population) and 6.8 million people (27.5% of the national population) lived in areas where, respectively, >1% and >10% of the school-aged children had M. perstans microfilaraemias. Since the prevalence of M. perstans microfilaraemia is known to increase with age, the overall population prevalences are likely to be even higher than the prevalences observed in the school-aged children. More attention needs to be paid to the public-health implications of this wide-spread but neglected infection.
Adolescent↗
Presence of Wolbachia endosymbionts in microfilariae of Wuchereria bancrofti (Spirurida: Onchocercidae) from different geographical regions in India.
In view of the recent discovery of rickettsial endosymbionts, Wolbachia in lymphatic filarial parasites, Wuchereria bancrofti and Brugia malayi and subsequently of their vital role in the survival and development of the latter, antibiotics such as tetracycline are being suggested for the treatment of lymphatic filariasis, by way of eliminating the endosymbiont. But, it is essential to assess their presence in parasites from areas endemic for lymphatic filariasis before such a new control tool is employed. In the present communication, we report the detection of Wolbachia endosymbionts in microfilariae of W. bancrofti parasites collected from geographically distant locations of India, such as Pondicherry (Union Territory), Calicut (Kerala), Jagadalpur (Madhya Pradesh), Thirukoilur (TamilNadu), Chinnanergunam (TamilNadu), Rajahmundry (Andhra Pradesh), and Varanasi (Uttar Pradesh), using Wolbachia specific 16S rDNA polymerase chain reaction.
Animals↗
Suppression of Brugia malayi (sub-periodic) larval development in Aedes aegypti (Liverpool strain) fed on blood of animals immunized with microfilariae.
Preliminary studies were carried out to investigate the role of filarial specific antibodies, raised in an animal model against the filarial parasite, Brugia malayi (sub-periodic), in blocking their early development in an experimental mosquito host, Aedes aegypti (Liverpool strain). In order to generate filarial specific antibodies, Mongolian gerbils, Meriones unguiculatus, were immunized either with live microfilariae (mf) of B. malayi or their homogenate. Mf were harvested from the peritoneal cavity of Mongolian gerbils with patent infection of B. malayi and fed to A. aegypti along with the blood from immunized animals. Development of the parasite in infected mosquitoes was monitored until they reached infective stage larvae (L3). Fewer number of parasites developed to first stage (L1) and subsequently to L2 and L3 in mosquitoes fed with blood of immunized animals, when compared to those fed with blood of control animals. The results thus indicated that filarial parasite specific antibodies present in the blood of the immunized animals resulted in the reduction of number of larvae of B. malayi developing in the mosquito host.
Aedes↗
Temporary shift of microfilariae of Brugia pahangi from the lungs to muscles in Mongolian jirds, Meriones unguiculatus, after a single injection of diethylcarbamazine.
A single-dose treatment with diethylcarbamazine (DEC) reduced microfilaria (mf) counts of Brugia pahangi by >90% at 30 min post-treatment in Mongolian jirds (Meriones unguiculatus). The reduction was followed by a rapid increase in microfilaremia, with the count reaching pretreatment level in 3 hr. The mechanisms behind this temporary reduction of mf were investigated. Without treatment, mf accumulated in the lungs. At 30 min post-treatment, they had moved from the lungs and accumulated in the muscle. At the same time, electron microscopy revealed many mf in the muscle interstitium. DEC concentrations at 30 min were much lower in the muscle (12.2 microg/g of tissue) than in the lungs, liver, and kidneys (19.8-40.7 microg/g), all of which declined to < 0.6 microg/g by 3 hr. The presence of mf in the muscle would be advantageous for avoiding high DEC concentrations, and their extravascular location could prevent attack by host effector cells.
Animals↗
The serpin secreted by Brugia malayi microfilariae, Bm-SPN-2, elicits strong, but short-lived, immune responses in mice and humans.
Understanding the basic immunology of an infectious disease requires insight into the pattern of T cell reactivity and specificity. Although lymphatic filariasis is a major tropical disease, the predominant T cell Ags of filarial species such as Brugia malayi are still undefined. We have now identified a prominent T cell Ag from B. malayi microfilariae (Mf) as Bm-SPN-2, a serpin secreted exclusively by this stage. Mf-infected mice mounted strong, but short-lived, Bm-SPN-2-specific Th1 responses, measured by in vitro production of IFN-gamma, but not IL-4 or IL-5, 14 days postinfection. By day 35, responsiveness to Bm-SPN-2 was lost despite enhanced reactivity to whole Mf extract. Single immunization with Mf extract also stimulated typical Th1 reactions to Bm-SPN-2, but IgG1 Ab responses dominated after repeated immunizations. Human patients displayed potent humoral responses to Bm-SPN-2 in both IgG1 and IgG4 subclasses. Thus, 100% (20 of 20) of the microfilaremic (MF(+)) patients bore IgG4 responses to Bm-SPN-2, while only 30% of endemic normal subjects were similarly positive. Following chemotherapy, Bm-SPN-2-specific Abs disappeared in 12 of 13 MF(+) patients, although the majority remained seropositive for whole parasite extract. PBMC from most, but not all, endemic subjects were induced to secrete IFN-gamma when stimulated with Bm-SPN-2. These findings demonstrate that Bm-SPN-2 is recognized by both murine and human T and B cells and indicate that their responses are under relatively stringent temporal control. This study also provides the first example of a stage-specific secreted molecule that acts as a major T cell Ag from filarial parasites and is a prime candidate for a serodiagnostic probe.
Animals↗
Intradermal reactivity of excretory and secretory products of onchocercal microfilariae.
The intradermal reactivity of excretory and secretory (ES) products derived from the in vitro cultivation of onchocercal microfilariae was evaluated. The ES products from Onchocerca volvulus were highly sensitive in the detection of active onchocerciasis in both Liberian and Guatemalan subjects. A low level of cross-reactivity occurred in patients with loaisis and in dogs with Dipetalonema reconditum, but not in dogs with Dirofilaria immitis. ES products from O. gutturosa evoked reactions in Guatemalan subjects, but were not as sensitive as those from O. volvulus.
Antigens↗
Extended cryopreservation of Mansonella ozzardi microfilariae concentrated from human peripheral blood.
Microfilariae of Mansonella ozzardi, concentrated from human blood, frozen with a cryoprotectant chemical, and stored at liquid or vapor-phase liquid nitrogen temperatures were motile when thawed after 2.5 years of preservation.
Brazil↗
The tail of the Mansonella streptocerca microfilaria.
Morphological studies of stained Mansonella streptocerca microfilariae from the skin of man and chimpanzees in West Africa revealed that the tail is bifid rather than blunt. This feature may be useful in characterization of related species.
Animals↗
Eosinophil hyporesponse of jirds induced by microfilariae of Brugia pahangi.
Male jirds (Meriones unguiculatus) were inoculated sc with 100 infective larvae of Brugia pahangi. After 16 weeks, the animals were reinoculated with a comparable number of organisms. Blood eosinophil responses during the 5 weeks subsequent to this attempt to reinfect were much lower than those of comparable naive animals, while the response to a heterologous infection (Toxocara canis) was comparable to that of controls. Mebendazole was given to infected animals for 2 weeks beginning 5 weeks (prepatent) or 16 weeks (patent) after infection. At comparable intervals after drug administration, the animals were reinoculated with infective larvae and the blood eosinophil response was measured over a 5 week period. The response in the animals treated during the prepatent period was higher than the untreated infected controls. Treatment during the patent period had no demonstrable effect. Jirds made artificially microfilaremic by intravenous inoculation of viable filaria before and after the standard infecting dose had a low eosinophil response to infective larvae. A primary experience of jirds with the microfilariae of B. pahangi evokes an eosinophil response. Subsequent inoculation of larvae did not produce a comparable response.
Animals↗
Killing effect of normal peritoneal exudate cells in guinea pigs on microfilariae of Dirofilaria immitis evoked by passive transfer of immune humoral factor.
Parasiticidal activity of normal peritoneal exudate cells on microfilariae of Dirofilaria immitis in diffusion chambers implanted into normal guinea pigs was evoked by intraperitoneal passive transfer of anti-D. immitis serum. The immune serum was fractionated into supernatant and sediment by ammonium sulfate precipitation. The parasiticidal effect was reproduced with the supernatant and, to a less extent, with the sediment. Anti-D. immitis serum from the animals sensitized 5 days before was also effective in this respect. From these results it can be concluded that the factor responsible for the phenomenon is some other factor(s) than the antibody. In addition, the in vitro cytotoxicity test demonstrated an enhanced Mf-killing activity of sensitized peritoneal exudate cells by adding with anti-D. immitis serum.
Animals↗
[Distribution pattern of Dirofilaria immitis microfilariae in peripheral blood of a dog and their intake by mosquitoes].
Experiments were made in which Aedes aegypti mosquitoes fed on a dog infected with Dirofilaria immitis, in order to determine the distribution pattern of microfilariae (Mf) in the dog's periphery blood and the number of Mf taken by the mosquitoes. Mosquitoes fed on an anesthetized dog at some 50 shaved skin spots and they were weighed immediately before and after feeding. This enabled us to examine not only the Mf number taken by each mosquito but also the Mf intake density in terms of Mf number per mg of blood. The Mf intake density showed a wide variation at the different parts of the dog's body, and the frequencies of Mf showed uneven distributions which were fitted best by the negative binomial. Significant differences were detected in the Mf intake density at different parts of the skin, but these differences were concluded as a non-consistent result because a similar result was not reproduced in the next experiment. It was presumed that not only the Mf number per mosquito but also the Mf intake density increased as the blood intake by the mosquitoes increased. This increase of both the Mf number per mosquito and the Mf intake density was also supported by another experiment in which mosquitoes were fed at the same skin spots consecutively one after another.
Aedes↗
Transmission in utero of microfilariae of Onchocerca volvulus.
Skin snips from newborn children and biopsy material from the umbilical cord and placenta of their mothers were examined. Microfilariae of O. volvulus were found in the skin of 2 out of 11 babies and in the umbilical cords of 2 out of 11 babies born to ten mothers infected with O. volvulus in Bawku Hospital, Ghana.
Female↗
Immunological cross-reaction between an Onchocerca paramyosin-like molecule and a microfilaria surface antigen.
A monoclonal antibody (2A5B9), previously shown to be reactive with a 14 kD surface associated antigen of Onchocerca microfilariae, was found to recognise a 92 kD molecule present in an adult worm extract. The antibody was used to select cDNA clones with a coding capacity larger than 14 kD, from a lambda gt11 library of O. volvulus. Nucleotide sequencing of the cDNA of one such clone revealed extensive homology to the myosin (unc-54) and paramyosin (unc-15) genes of Caenorhabditis elegans, similarly to myosin and paramyosin genes of Onchocerca volvulus, Brugia malayi, Dirofilaria immitis and Schistosoma mansoni. The immunological implications of antigenic cross-reactivity between a surface molecule and paramyosin, a known protective antigen, are discussed.
Amino Acid Sequence↗
Onchocerca volvulus: in vitro killing of microfilaria by neutrophils and eosinophils from experimentally infected chimpanzees.
Peripheral blood leukocytes from chimpanzees experimentally infected with third stage larvae, or with nodular microfilaria (mf) of Onchocerca volvulus, were evaluated for their ability to kill nodular mf in vitro. Inoculation of chimpanzees with third stage larvae, and prospective follow up, permitted each animal to be classified as patent, infected but not patent, or post-patent. Neither lymphocytes nor monocytes significantly adhered to, immobilized, or killed mf. However, neutrophils or eosinophils killed mf effectively in the presence of immune serum. Neutrophil and eosinophil enriched cell preparations from control animals were able to kill mf with serum from infected animals, but to a significantly lesser degree than when both cells and serum were taken from infected animals. Chimpanzees inoculated with mf showed a progressive increase in cellular killing of mf after a second inoculation which surpassed that seen with animals inoculated with third stage larvae. Antibody-mediated killing of mf by neutrophils and eosinophils may be important in the termination of patency in this infection.
Animals↗
Immunity to Onchocerca volvulus microfilariae in mice and the induction of cross-protection with O. lienalis.
Inbred CBA/Ca mice were vaccinated with Onchocerca volvulus or Onchocerca lienalis microfilariae (mf) and challenged 100 days later with the homologous or heterologous parasite. There was a major reduction in mf recoveries from immunised animals compared with controls when the sensitising and challenge infections were both of O. volvulus mf. Resistance was manifest within one week of challenge, and rose from an 87% reduction in recoveries on day 7 to a 96% reduction on day 15. Similar results were obtained for homologous sensitising and challenge infections with O. lienalis mf. Protection afforded by sensitisation with the heterologous parasite was also high, although the expression of resistance appeared to be delayed. Vaccination with O. lienalis mf led to a 45% level of cross-protection against O. volvulus at 7 days after challenge, which rose to 94% by day 15. Vaccination with O. volvulus mf stimulated cross-protection against O. lienalis at levels of 49% and 80% as measured 7 and 15 days after challenge. It is concluded that the mouse model may be of value in analysing immune responses directed against O. volvulus mf and that the cross-protection between Onchocerca species is an advantage that should be exploited in characterising the antigens involved.
Animals↗