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At least 19 recordsLinked to original sources
PubMed1992

Cloning and characterization of a Loa loa-specific repetitive DNA.

A Loa loa EcoRI genomic library in lambda gt11 was screened with 32P-labeled L. loa DNA and 1 repetitive clone, LL20, was isolated. An 800-bp Rsa I fragment of LL20, which is L. loa specific, was subcloned into pUC19 and the recombinant plasmid was designated pRsa4. While the 3.8-kb Eco RI fragment of LL20 cross-hybridized to other filarial DNA under low stringency conditions, the 800-bp fragment of pRsa4 was L. loa specific under the same conditions. Further characterization of the insert of pRsa4 was therefore carried out. Its lower limit of detection is 800 pg of L. loa genomic DNA, it has a low copy number (50-100) and an interspersed distribution in the genome. As a probe it does not distinguish between simian and human L. loa DNA. The nucleotide sequence contains 69% A + T and 31% G + C and shows no notable internal repeats.

Animals↗
PubMed1987

Filariasis due to Loa loa and Mansonella perstans: distribution in the region of Okondja, Haut-Ogooué Province, Gabon, with parasitological and serological follow-up over one year.

The prevalence of Loa loa and Mansonella perstans filariasis has been determined in 6 rural villages in eastern Gabon. Between 18.9 and 27.2% of people carry L. loa microfilariae with an overall microfilarial rate of 25.1%. The microfilarial rate for M. perstans was more variable, between 33.3 and 62.2% (average 49.1%). No significant difference was seen in the microfilarial rate with age over 15 years for either parasite, but men were infected more frequently than women. Anti-L. loa antibody titres were measured, using a homologous microfilarial antigen in ELISA. Taking the parasitological and immunological evaluations together, only 10% of the sample population appear to be free of these filarial infections. L. loa and M. perstans microfilaraemia and corresponding serology were also investigated twice in 150 people at a one-year interval. 99.1% of the cases who had no circulating L. loa microfilaria in March 1984 still did not show any 12 months later. Similarly, 97.1% of the untreated, microfilaraemic cases still harboured this parasite a year later. The same was not observed for M. perstans, since microfilariae appeared or disappeared in 26.7% of the cases. This suggests different dynamics for the two filarial infections. Variation in individual anti-L. loa antibody titres was low. The possibility of a genetic influence on the expression of loiasis is discussed.

Adolescent↗
PubMed1992

Antibody-dependent cell-mediated immune reactions to Loa loa microfilariae in amicrofilaraemic subjects.

Antibody-mediated mechanisms that could be important in controlling microfilaraemia in Loa loa infected amicrofilaraemic adults (mf-ve) were studied. These subjects were selected as having a verified ocular passage of an adult L. loa but being amicrofilaraemic and without recent diethylcarbamazine treatment. Sera from 37 mf-ve subjects were compared to 14 sera from heavily (greater than 4000 mf/ml) infected subjects (mf+ve) and 9 sera from Caucasian control subjects for their reactions with L. loa mf (mf). Many mf-ve sera (22/37) were strongly positive in immunofluorescence (IFAT) on living mf. Mf+ve sera were negative, or only weakly positive, and Caucasian sera were negative. Clinical signs were not significantly different between IFAT reactive and non-reactive mf-ve subjects. Approximately half of the IFAT positive, mf-ve sera were also able to agglutinate mf; no other sera were active in this test. Titres ranged from log2 3-6 and in most cases, 9/11, the agglutination reaction was mercaptoethanol-sensitive. Antibody-dependent cellular adherence was studied using mf and leukocytes from uninfected donors. Using cryopreserved mf many heat-inactivated mf-ve sera gave strong reactions with obvious adherence by 4 h and few motile mf remained by 16 h but when fresh mf were employed these reactions were weak. However, addition of complement to many (10/11) mf-ve sera considerably enhanced adherence to fresh mf. The effect of various treatments on the complement source indicated a role for both the classical and alternative pathways. The cells attached to mf were mainly neutrophils (83%) with some eosinophils (15%) and few mononuclear cells (2%). The common occurrence of antibodies able to mediate complement-dependent adherence of polymorphonuclear leukocytes to L. loa mf in the sera of mf-ve subjects may indicate that such a mechanism is important in controlling microfilaraemia in vivo.

Adult↗
PubMed1975

Loa loa: development to the infective stage in an American deerfly, Chrysops atlanticus.

Chrysops atlanticus, an American species of deerfly collected along the Mississippi Gulf Coast, will support the development of the microfilaria of human Loa loa to the infective stage. Development takes place in the fat body of the fly and requires 9 to 10 days of development and pattern of morphogenesis of the parasite in C. atlanticus is virtually identical to that described in natural African vectors. Chrysops atlanticus will support the development of large numbers of L. loa to the infective stage without apparent ill effects. Two uninfected patas nonkeys each were given 75 third-stage larvae obtained from experimentally infected C. atlanticus. Both animals developed patent infections in approximately 5 months, clearly demonstrating that the entire life cycle of Loa loa can be maintained in the laboratory outside endemic areas.

Animals↗
PubMed1990

Macaca fascicularis, a nonpermissive host for the human filarial parasite Loa loa.

The ability of the filarial nematode Loa loa to infect 2 species of primates was studied. The primate species selected were closely related to species known to be susceptible. A mandrill (Mandrillus sphinx) and 6 cynomolgus monkeys (Macaca fascularis) were infected by subcutaneous injection of third-stage larvae of human L. loa from Gabon. The mandrill developed microfilaremia with an estimated prepatent period of 147 days, but microfilariae were not detected in any of the cynomolgus monkeys. Thus, mandrills appear permissive to human L. loa, whereas cynomolgus monkeys are not. Serum antibody responses were examined on western blots of adult L. loa antigens. Preinfection sera from all animals gave no reactions, but, after infection, sera from cynomolgus monkeys reacted more intensely and with more antigens than mandrill sera. Antibodies were still detectable in cynomolgus monkeys 15 mo postinfection. These reactions were compared with those found using human infection sera. Reactions with the cynomolgus monkey sera resembled those found with resistant endemic and amicrofilaremic human sera.

Animals↗
PubMed1979

[Cameroon swelling; infection by the filaria Loa loa].

Recurrent skin edemata due to an infestation with the filaria Loa loa are called Cameroon or Calabar swellings. These are tense elastic, circumscribed, indolent swellings, which are just slightly red coloured and disappear within 24 to 48 hours. Intervals of several weeks or months may occur. One should think of Loa loa disease seeing travellers return from Loa endemic areas (West Africa) with recurrent, transitory edema and eosinophilia. The stay in these areas may have been several years before! Treatment and prophylaxis: Diethylcarbamazine.

Cameroon↗
PubMed1988

Identification of a surface antigen on Loa loa microfilariae the recognition of which correlates with the amicrofilaremic state in man.

Filarial infections induce a spectrum of disease in their natural hosts, and by correlating immunity found in individuals with their disease pattern, one may delineate non-pathogenic, protective mechanisms. Loa loa is causal of mild to moderate pathology, and it is unique among the human filaria in that adult worms are occasionally visible during subconjunctival migration. To study immune mechanisms controlling microfilaremia, sera from 15 subjects with amicrofilaremic occult loiasis (OL) were compared with sera from 10 subjects with microfilaremic loiasis (ML) microfilaremia, (greater than 4000/ml) for their reactions with living microfilariae (mf). An IFA was first used to detect antibodies able to bind to the surface of living L. loa mf. ML subjects either did not react (7/10) or reacted only very weakly (3/10). Highly reactive sera were found only in OL subjects; 7/15 gave very bright fluorescence, 5/15 gave moderate reactions, and 3/15 were negative. Most of these antibodies were of the IgG class. Sera from all subjects were also reacted with living mf in an antibody-dependent cellular adherence test using normal leukocytes. Sera that were strongly positive in IFA showed strong adherence and IFA-negative sera were non-reactive. To identify the Ag involved, mf were surface iodinated, detergent-extracted Ag were immunoprecipitated, and Mr was determined on SDS-PAGE. Several OL sera, all highly reactive in the above tests, precipitated a 23-kDa molecule with which all ML sea failed to react. Sera from a mandrill experimentally infected with L. loa also precipitated the 23-kDa Ag when taken post-patency. In conclusion, it appears that certain people who control L. loa microfilaremia have high levels of IgG antibodies that bind to a surface Ag of 23 kDa and are able to mediate cellular adherence.

Adhesiveness↗
PubMed1989

Hypogonadism and ecdysteroid production in Loa loa and Mansonella perstans filariasis.

Possible endocrinological repercussions of infection with Loa loa and Mansonella perstans filariae were studied in Gabonese subjects. Microfilaremic males were compared with amicrofilaremic controls. In the infected group 13/105 subjects (12%) presented only abnormally low serum levels of testosterone (less than 4 ng/ml), 25/105 (24%) only abnormally high serum levels of gonadotrophins, FSH (greater than 15 mIU/ml) and LH (greater than 20 mIU/ml), and 22/105 (21%) presented anomalies in both testosterone and gonadotrophin levels. One out of 68 control subjects had 3.6 ng/ml seric testosterone and all had normal levels of gonadotrophins. Ecdysteroids were detected (greater than 0.025 ng/ml) in the serum of 87/97 (90%) microfilaremic subjects (GM 0.123 ng/ml) compared to 12/64 (19%) controls (GM 0.030 ng/ml). Ecdysteroids were detected in the urine of all subjects, infected (GM 8.468 ng/ml) as well as control (GM 1.245 ng/ml). The hormonal perturbations were correlated with the levels of Loa loa microfilaremia but not with those of serum and urinary ecdysteroids. These results demonstrate that microfilaremic subjects often show endocrinal signs of hypogonadism and present appreciable levels of ecdysteroids in serum and urine. A direct role for parasitic ecdysteroids in hypogonadism remains to be demonstrated.

Adult↗
PubMed1988

The identification and partial characterization of an immunodominant 29-31 kilodalton surface antigen expressed by adult worms of the human filaria Loa loa.

Detergent solubilized extracts of 125Iodogen surface labelled adult Loa loa revealed a relatively simple profile consisting of a strongly labelled molecule at 29-31 kDa and weakly labelled molecules at 14.5, 17, 21, 23, 34, 58, and 86 kDa. Residents of a L. loa endemic zone were assessed clinically and parasitologically and classified as microfilaremic, amicrofilaremic with documented ocular passage of adult worms, or 'resistant' subjects without any signs of infection. Sera from these subjects were used to identify L. loa adult surface antigens. All 'resistant' sera immunoprecipitated the 29-31 kDa antigen although some were more strongly reactive than others. The amicrofilaremic sera strongly immunoprecipitated the 29-31 kDa antigen, whereas microfilaremic sera reacted weakly or not at all with this antigen. Longer exposures of immunoprecipitates of strongly reactive sera revealed the recognition of additional antigens of 86, 44, 34, 23, 21, 17 and 14.5 kDa. Studies with heterologous sera demonstrated that these antigens contain cross-reactive epitopes which are restricted to filarial parasites. Biochemical characterization of the predominant 29-31 kDa antigen showed that it bound concanavalin A, was sensitive to proteases, and its antigenicity was resistant to heat but sensitive to periodate and endo-beta-N-acetylglucosaminidase H. These observations suggest that it is a glycoprotein containing mannose and N-acetylglucosamine residues and that the carbohydrate moiety is important for antibody binding. The importance of the 29-31 kDa glycoprotein in the immunobiology of loaiasis is suggested by the finding that resistant and infected amicrofilaremic individuals have strongly reactive IgG antibodies to this antigen.

Animals↗
PubMed1991

Effect of attraction factors on the sampling of Chrysops silacea and C. dimidiata (Diptera: Tabanidae), vectors of Loa loa (Filaroidea: Onchocercidae) filariasis.

The effects of fire and human host density on Chrysops silacea and C. dimidiata abundance and age structure was evaluated at sites of Loa loa filariasis transmission in the Congo rain forest. Fire increased the catch of C. silacea 8.5-fold at ground level and 5-fold in the canopy, but did not modify the catch size of C. dimidiata. Catch size increased 2-fold when a pygmy camp located near the collecting station was inhabited. The presence of fire did not alter the parity and Loa loa infection rates in the populations.

Animals↗
PubMed1989

Differential recognition of Loa loa antigens by sera of human subjects from a loiasis endemic zone.

Somatic antigens of Loa loa adult worms with molecular weights of 15-180 kDa were identified by Western blot analysis using sera from 3 categories of parasitologically and clinically defined subjects from a loiasis endemic zone. Sera of occult, amicrofilaremic (OL), and 'resistant' individuals with no clinical signs of infection (R) reacted with an antigen of 160 kDa; sera of highly microfilaremic individuals (ML) did not. ML sera strongly reacted with an antigen of 18 kDa which was recognized only weakly or not at all by OL and R sera. At higher dilutions, OL sera only reacted with antigens at 23 and 160 kDa and ML sera reacted with antigens at 18 and 23 kDa, whereas R sera reacted with antigens at 23, 42, 54, 70, 100, and 160 kDa. These data suggested that R sera contained a higher concentration of antibodies which reacted with denatured, nitrocellulose-bound antigens. The IgG4 isotype predominated for all groups of sera, while IgG3 antibody responses were observed only with R sera. IgG1 antibodies were seen in all groups but reacted with fewer antigens than IgG4 antibodies, and no IgG2 antibody responses were detected. Sera against Brugia malayi, Wuchereria bancrofti, Onchocerca volvulus, and Dirofilaria immitis cross-reacted with somatic antigens greater than 70 kDa, whereas none reacted with Loa loa antigens less than 23 kDa.

Animals↗
PubMed1977

Loa-loa microfilaremia in the Nigerian population.

In about half of 1026 Nigerians infected with Loa loa, the microfilaria levels were low, less than 8% had more than 1000 microfilariae in 50 cumm blood. The length range of 445 microfilariae obtained from 39 infected people was 156.8 to 308.7 micron with a mean of 236.4 micron, or microgram; smaller than in the Kumba strain of Cameroon. The persistence of a rather high number of microfilariae in the peripheral blood of four patients till 22 hours was discussed in relation to the importance of Mansonia africana mosquitoes as a vector of Loa loa.

Adult↗
PubMed1985

Loa loa: development and course of patency in experimentally-infected primates.

Loa loa infections were studied in baboons, rhesus and patas monkeys. Animals were infected either by s.c. injection of third-stage larvae (L 3) or by surgical implantation of juvenile worms of known age, sex and number. Microfilaremia was first detected in baboons at 140 days following inoculation of L 3 and at 142 days and 143 days in patas and rhesus monkeys, respectively; the mean prepatent period was 151 days in baboons, 149 days in patas monkeys and 169 days in rhesus monkeys. The primary wave of microfilariae (mf) was suppressed by the spleen in all three primate species. In baboons, the initial wave of mf lasted from 11 to 46 weeks (mean: 22 weeks), whereas in patas monkeys it persisted for 47 to 60 weeks, and in rhesus monkeys for 1 to 2 years. Gross and microscopical changes in the spleen were noted in all three primate species and consisted of numerous granulomata in the red pulp underlying the capsule. A resurgence of mf was observed following splenectomy in all three species of monkeys. Postsplenectomy levels of microfilaremia typically exceeded presplenectomy levels. One pair of worms was sufficient to produce patent infections in monkeys for extended periods of time. However, levels of microfilaremia were lower than in monkeys which received 75 and 200 to 300 L 3, although some overlap in microfilaremias between groups did occur. Overall, there was no proportional relationship between levels of microfilaremia and numbers of adult worms recovered from monkeys at necropsy. It was observed that, in the primate host, Loa is a long-lived parasite. Living worms were recovered from the tissues as long as 9 years after inoculation and there was no reason to doubt that patency would have persisted for some time into the future. Adult worms were frequently observed moving freely in the subcutaneous tissues of the primate hosts, although no instance of Calabar swellings or the presence of worms in or around the eye were ever recorded. The primate model of loiasis is an especially useful system because of the predictability of the behavior of the parasite. In most regards, the behavior of L. loa in the primate host is comparable to observations on the parasi e in man.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1977

[Etiological study of low fertility in eastern Gaboon. III. Filarial endemicity (Loa loa, D. perstans). Prevalence of microfilariae in hydroceles (author's transl)].

During an inquiry performed in Gaboon the prevalence of hydroceles had led to puncture systematically every vaginal flow. 68 fluids were so collected at the end of the inquiry. Subsequently the statistical analysis of the results in men seems to suggest a correlation between microfilaremia (Loa loa and D. perstans) and the prevalence of hydroceles. Microfilariae were found in 77% according to the following distribution: Loa loa seldom diagnosed in this kind of flow were detected in 10%; D. perstans although never reported so far in hydrocele fluids appeared to be present in 62%. O. volvulus more currently referred to in hydrocele liquids were scarcely traced.

Adult↗
PubMedDate not supplied

Loa loa and Mansonella perstans filariasis in the Chaillu mountains, Congo: parasitological prevalence.

1934 Bantus and 379 Pygmies were investigated for Loa loa and Mansonella perstans filariasis in 7 villages in the Chaillu forest of the Congo. Bantus were more frequently infected with L. loa than Pygmies (18.9% of microfilariae carriers compared with 10.6%). In individuals over 30 years of age, males were more frequently infected than females. Microfilarial densities increased until the age of 20 years and then remained stable. Parasite load was not significantly different in the two ethnic groups. For mansonelliasis, the microfilarial rate was higher in the Pygmies (67.5% compared with 22.0%) and males of the 2 groups were more frequently infected than females. Microfilarial load was also higher in Pygmies than in Bantus (mean microfilarial densities (MfD 50) 13 and 2 respectively). In the Pygmy group, MfD 50 for M. perstans increased with age whereas it remained stable in the Bantus. 53.8% of the 249 questioned persons had experienced worm migration under the conjunctiva. Both ethnic groups were equally exposed to the vectors of L. loa and reasons for the difference in prevalence of microfilaria carriers are discussed. For mansonelliasis increased contact with vectors may explain the higher degree of infestation observed in Pygmies. Other filariases were infrequent in (Mansonella streptocerca), or absent from (Onchocerca volvulus and Wuchereria bancrofti), the study area.

Adolescent↗