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PubMed1991

[Observations on the development of quantitatively inoculated Brugia malayi microfilariae in Anopheles sinensis and Culex quinquefasciatus].

With an improved technique, quantitative inoculation of Brugia malayi microfilariae (mff) into Anopheles sinensis and Culex quinquefasciatus was carried out in our laboratory in 1988. The development of B. malayi mff in these two species of mosquitoes was observed. In the system of B. malayi and An. sinensis, a well-fitted linear correlation appeared between the number of mff inoculated and the infective larva (L3) positive rate (r = 0.9910; P less than 0.01). The regression equation with the regression coefficient of 8.490 suggested a high susceptibility of this species of mosquito to B. malayi even under the condition of experimental inoculation. The quantitative relationship between the number of mff inoculated and the average filarial maturity rate was also exhibited. At the same dosages of 4 and 10 mff/mosquito, the L3 positive rates and the average filarial maturity rates in An. sinensis were much higher than those in Cx. quinquefasciatus (P less than 0.01), indicating significant difference occurred inside the bodies of these two species of mosquitoes.

Animals↗
PubMed1991

Migration and death of skin-dwelling Onchocerca volvulus microfilariae after treatment with ivermectin.

The effects of a single dose of ivermectin (122-200 micrograms/kg) on Onchocerca volvulus microfilariae (mf) in skin and lymph nodes were studied histologically in a qualitative and quantitative manner over seven days after treatment. Ivermectin caused mf to move from the subepidermal layer into the deeper layers of the dermis, subcutaneous fat and connective tissue, and the regional lymph nodes. No mf were seen migrating upwards through the epidermis. Dead mf were not seen before 24 hr and the numbers found dead in the dermis were far fewer than the total numbers in the skin before treatment. Inflammatory cellular reaction around dead mf in the tissues was usually minimal. The results suggest that most of the mf which disappear from the skin may be destroyed in the lymph nodes and that the histological reaction excited by mf dying under ivermectin is less violent than that after diethylcarbamazine.

Adult↗
PubMed1991

The effects of ivermectin on the viability of Onchocerca lienalis microfilariae in vitro and on their subsequent development in the blackfly vector, Simulium ornatum.

Experiments examined the sensitivity of Onchocerca lienalis microfilariae (mf) to ivermectin in vitro using a range of parameters to measure viability. Incubation in drug (1 x 10(-4) and 5.71 x 10(-8) M) caused an immediate decrease in motility levels in a concentration dependent fashion with a continuing decline over 24 h; the inclusion of a monkey kidney cell (LLCMK2) feeder layer in the culture system partially abrogated drug effects. The use of feeder cells allowed the longer-term culture of mf; incubation in drug at low concentrations (5.71 x 10(-8) and 1 x 10(-10) M) significantly reduced motility levels during a 17 day trial. Using MTT colorimetry it was found that 10,000 untreated mf per replicate sample were required to produce a sufficient quantity of formazan to make comparisons, and that formazan formation was most rapid during the first 30 min of incubation in MTT but continued up to 3-4 h. Following incubation of mf in ivermectin (1 x 10(-4) and 5.71 x 10(-8) M) for 24 h, only the higher concentration inhibited formazan formation (51%), while motility levels were reduced by 94% and 45% respectively. Using the same drug concentrations, mf viability was assessed by measuring the uptake of [3H]2-deoxy-D-glucose; uptake was only significantly reduced (40%) by the higher concentration, while motility levels were reduced by 77% and 63% respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effect of ivermectin on the vertical distribution of Onchocerca volvulus microfilariae in the skin.

A new technique for assessing vital and degenerative microfilariae (mf) in different skin layers of onchocerciasis patients is described. Vertical sections at least 5 mm deep were collected from the surgical nodulectomy wounds before and 2, 4 and 28 days after treatment with ivermectin and fixed in ethanol. Skin biopsies were punched horizontally with trephines and digested enzymatically with collagenase. In untreated biopsies 80% of the mf were located in the uppermost layer of 1 mm and only 1.2% were degenerated. After treatment with ivermectin the total number of mf was significantly reduced, and the distribution of living and remnant mf in the different skin layers had changed. The proportion of degenerated mf had increased markedly, but did not exceed 6% of the total pre-treatment mf level, i.e., the vast majority of the mf had actually disappeared from the skin. It is suggested that ivermectin reduces microfilarial motility slightly, and that mf are then attacked by adhering immunocompetent cells of the host and cleared by the lymphatic drainage.

Animals↗
PubMed1989

Dynamics of microfilariae of Onchocerca volvulus over the first 72 hours after treatment with ivermectin.

Changes in microfilaria (mf) densities in skin, blood and urine were followed over 72 hours in 8 Guatemalan patients who received invermectin (150 mcg/kg po in a single dose). After an initial increase at 6 hours, the significance of which is not clear, mf densities in skin snips decreased rapidly to reach 13% of their pre-treatment level by 48 hours and then fell much more slowly over the next 24-hour period. The fall in mf concentrations is thought to be mainly a result of movement away from the subepidermal layer. In contrast to what happens after DEC, it was not accompanied by any marked wave of microfilaraemia or microfilaruria, nor by the appearance of a papular rash, although brawny oedema of the skin sometimes developed. Reactions that occurred after ivermectin could not be correlated with the initial density of microfiladermia. It is hypothesized that the movement of mfs may be 1) into the deeper layers of the dermal collagen, 2) the subcutaneous fat, or 3) the lymphatic system.

Adult↗
PubMed1989

[The inner body of Loa loa microfilariae. Morphologic and physiopathologic data].

The innenkörper is visible in 80% of the cases of microfilariae Loa loa we have studied and stained at pH 7.2. In thick blood film, however, it was not visible. It lies between the middle of the body and the G1 = R1, cell. The central viscus rarely take the form of a single elongated mass, it most often appears moniliform with 2 to 5 granular masses and it is sometimes reduced to a few number of granulations. Its average length is 34 microns. As with W. bancrofti it would appear to have the role of a nutritional reserve.

Animals↗
PubMed1989

[Cryopreservation of microfilariae and third-stage larvae of Brugia malayi and subsequent development in the hosts].

Methods are studied for the cryopreservation of microfilariae (mf) and third-stage larvae (L3) of periodic Brugia malayi. RPMI-1640 tissue culture medium containing 6% dimethyl sulfoxide (DMSO) and 15% newborn calf serum were used as cryoprotectant. The larvae survived best when specimens were frozen at the rate of -0.5 degrees C to -1.0 degrees C per minute using the vapor phase of liquid nitrogen, when the temperature reached -70 degrees C to -90 degrees C the specimens were placed directly into the liquid nitrogen (-196 degrees C). After the thawing of the mf which had been stored for 6,212 and 375 days in cryogen, 96.2% of the mf were shown to be viable and developed in Aedes togoi. It was also shown that the survival rate of L3 cryopreserved for 28-321 days was also 96.2% and that, when 107 L3 frozen for 321 days were inoculated after being thawed into one jird, one live female adult was recovered at autopsy 71 days after inoculation, its morphology being the same as the unfrozen specimens. There was no correlation between the time of cryopreservation and the survival rate of the larvae.

Aedes↗
PubMed1987

Lectin binding to the developing forms of Onchocerca gutturosa microfilariae.

Uterine and skin derived forms of microfilariae (mf) and earlier developing stages of the cattle filarial nematode Onchocerca gutturosa were examined for the lectin binding properties of their external surfaces (ie. egg shell and microfilarial cuticle). Both the uterine and skin derived forms of mf failed to bind any of the lectins tested. Incubation in known microfilaricides did not promote any binding of lectins to these parasites. Peanut agglutinin (PNA) was the only lectin found to bind specifically to earlier developing stages (i.e. the shells of freshly obtained eggs). Diethylcarbamazine (DEC) did not alter the binding pattern from that observed in untreated eggs. Ivermectin eliminated PNA binding but increased Ricinus communis lectin (RCA-1) positivity. Trypsin, collagenase and protease enzymes all affected the binding; chitinase however did not have any effect. These results support the concept that the eggshells of filariae can interact with the host defence responses.

Animals↗
PubMed1988

The skin-dwelling microfilariae of Monanema martini in Lemniscomys striatus as potential drug screening model for onchocerciasis: midazolam effect in vitro.

The murid model of Monanema martini in Lemniscomys striatus was used to evaluate its potential as drug screening model in onchocerciasis. It had been described that the histopathology and the reaction to diethylcarbamazine treatment of this model closely resemble human onchocerciasis. To study further similarities the in vitro effect of midazolam was examined. Skin-dwelling microfilariae (mf) of M. martini were taken by skin snips and placed in either plain phosphat buffered saline or midazolam. Concentrations of 50 micrograms/ml midazolam significantly reduced motility within 15 min. The percentage of fully motile mf dropped to 9.2 and 1.4 after 15 and 30 min, respectively. In contrast to this finding fully motile mf were obtained after intraperitoneal injection of 60 mg/kg BW; but the technique used did not allow to evaluate the in vivo effect of midazolam. The similarities with the human disease and the finding that midazolam paralyses mf of M. martini like mf of O. volvulus in vitro indicate the potential of the model for simulating human onchocerciasis.

Animals↗
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↗
PubMed1988

Suppression of release of microfilariae in vitro from Setaria cervi (Nematoda: Filariodeae) by chlorpromazine.

Chlorpromazine (CPZ) caused suppression in release of microfilariae in vitro from Setaria cervi at 10(-5) M concentration. The inhibitory effect of CPZ was further stimulated by Ca2+ (2 mM), whereas addition of EGTA (2 mM) resulted in partial reversal. Addition of dopamine (1 mM) along with CPZ (10(-5) M) caused similar inhibition as was observed in the presence of CPZ (10(-5) M) alone. CPZ did not effect in vitro oxygen uptake by worm homogenates up to 0.5 mM concentration. The results indicate the Ca2+/calmodulin-dependent anthelmintic action of CPZ on S. cervi.

Animals↗
PubMed1988

Experimental ocular onchocerciasis in cynomolgus monkeys. III. Roles of IgG and IgE antibody and autoantibody and cell-mediated immunity in the chorioretinitis elicited by intravitreal Onchocerca lienalis microfilariae.

Intravitreal injection of small numbers (10-500) of microfilariae (Mf) of Onchocerca lienalis in eyes of cynomolgus monkeys induces posterior segment lesions which resemble those occurring in human onchocerciasis in some respects. In order to determine the potential roles of antibody and cell-mediated immune responses in the formation of these lesions, anti-Onchocerca and anti-retinal IgG and IgE antibody and peripheral lymphocyte blastogenic responses were followed in eight monkeys, for one week to five months after intravitreal injection of Mf. Significant ocular inflammation occurred well before any antibody or peripheral lymphocyte blastogenic responses could be detected. It may be that direct effects of Mf, e.g., by activation of complement via the alternative pathway fulfill important roles in the pathogenesis of the posterior segment lesions.

Animals↗
PubMed1988

Factors influencing the ingestion of Onchocerca cervicalis microfilariae by Culicoides variipennis (Diptera: Ceratopogonidae).

Culicoides variipennis were fed under controlled conditions on two ponies that exhibited seasonal changes in Onchocerca cervicalis microfilarial (mf) skin density and skin distribution. The seasonal changes did not radically affect mf ingestion. Flies were fed on the umbilicus of infected ponies by two methods: individual feeding in consecutive order at the same site, or by mass feeding. Linear regression analysis indicated that ingestion of microfilaria was independent of feeding time and engorged weight. In the individual feeding data, there was a trend toward an increased ingestion of mf as the feeding time increased. Mass feeding trials suggest early feedings by C. variipennis may influence mf ingestion rates of flies that feed on subsequent days. Of the 1,104 flies feeding on both ponies over a 2-year period, 220 (20%) ingested mf and 99 (9% of all engorged flies) ingested only one mf.

Animals↗
PubMed1988

Efficacy of ivermectin in paste and injectable formulations against microfilariae of Onchocerca cervicalis and resolution of associated dermatitis in horses.

The efficacy of a single dose of ivermectin (0.2 mg/kg), in injectable or paste formulations, against microfilariae of Onchocerca cervicalis and associated skin lesions was evaluated in 20 naturally infected horses during midsummer months in Louisiana. All horses had clinical signs of dermatitis of the ventral midline and/or limbs, shoulders, thorax, and withers. Efficacy was monitored at 21, 42, and 63 days after treatment. Procedures done at these intervals included microfilarial counts of 6-mm skin biopsy specimens of affected ventral midline, grading of gross lesions, and photography and histologic assessment of ventral midline biopsy specimens. Microfilarial numbers were reduced to 0 by 21 days after treatment in all but one horse. Active lesions improved or were resolved completely by 63 days after treatment. Total inflammation, as judged by histologic methods, was reduced in all horses by 63 days after treatment, but there was a residual population of inflammatory cells in all horses. Adverse reactions after treatment were not observed in any of the horses.

Animals↗
PubMed1988

The effect of diethylcarbamazine on the in vitro serum-mediated adherence of feline granulocytes to microfilariae of Brugia pahangi.

The effect of the antifilarial drug diethylcarbamazine (DEC) on immunologically mediated destruction of the microfilariae (mf) of Brugia pahangi in vitro is addressed by studying the drug's influence on the granulocyte adherence to the surface of mf and the subsequent death of these parasites. DEC enhanced the adherence of cat blood-derived granulocytes to the surface of mf through the meditation of cuticle direct antibodies but not that mediated by complement alone; the parasites became immobilized and degenerated subsequent to cell adherence. The rate of cell adherence in the antibody-containing cultures was enhanced by DEC. As previously reported, this drug had no direct effect on the viability of the parasites. Preincubation of the cells in DEC had a greater effect on cell adherence than did preincubating the parasites in the drug, thus supporting the contention that this antifilarial compound may act on host components. Further investigation of this possibility may contribute significantly to a more complete understanding of why DEC can cause severe side reactions in filariae infected patients.

Animals↗
PubMed1988

Autoantibody induced by experimental Onchocerca infection. Effect of different routes of administration of microfilariae and of treatment with diethylcarbamazine citrate and ivermectin.

Hartley guinea pigs were injected with microfilariae (Mf) of Onchocerca lienalis as a model for acute inflammatory responses to Mf in human Onchocerca volvulus infection. IgG autoantibody reactive with a 3 M KCl extract of guinea pig cornea was detected by ELISA in the serum of guinea pigs injected with O. lienalis Mf three or more times sub-conjunctivally, or two or more times subcutaneously. Administration of the microfilaricides diethylcarbamazine citrate and ivermectin did not alter the proportion of animals expressing autoantibody or the mean autoantibody titer. The severity of acute corneal inflammatory reactions to Mf was similar in animals with and without circulating autoantibody. Although autoantibody responses did not correlate with acute corneal inflammatory reactions to dead Mf, the ability of Mf to induce formation of an antibody reactive with a component of autologous cornea suggests that autoimmune mechanisms might participate in chronic onchocercal lesions in the cornea, eg, sclerosing keratitis.

Animals↗
PubMed1987

The reduction in microfilariae loads in the skin and eye after nodulectomy in Ecuadorian onchocerciasis.

This study is concerned with the relationship between palpable onchocercal nodules and Onchocerca volvulus microfilarial loads in the skin. The number of microfilariae in clinically normal skin decreases as the distance from the nodule increases. Surgical removal of nodules reduces the microfilarial loads in 40 of 46 patients studied over a period of five months, with an average reduction of 65.4% of the prenodulectomy microfilarial load at the iliac crest. Complete elimination of detectable parasites was seen in some patients. Five individuals had increased microfilarial loads, all of which had developed new palpable nodules. Also, nodulectomy had a significant effect on ocular tissue, reducing the levels of parasites in the cornea and anterior chamber in 10 of 15 patients observed with no new nodules developing during the observation period. Both dermal and ocular clinical manifestations of onchocerciasis were reduced in a proportion of the patients. These parasitological and clinical findings provide evidence that nodulectomy is a beneficial procedure to O. volvulus infected patients in Ecuador by reducing both microfilarial loads and the degree of pathology.

Animals↗