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Biomedical subjects

M L Eberhard

Publications and source records attributed to M L Eberhard.

At least 109 records · Page 6Linked to original sources
PubMed1990

Dracunculus insignis in ferrets: comparison of inoculation routes.

Three routes of inoculation were compared to determine the best method to infect ferrets with Dracunculus insignis. The traditional method of administering infected cyclops containing L3s through gavage was compared to intraperitoneal (i.p.) and subcutaneous (s.c.) inoculation of L3s. Ten of 18 (56%) gavaged ferrets became infected after receiving copepods containing approximately 100 L3s each; 44 adult worms were recovered from these 10 animals. Twenty-one of 28 (75%) animals inoculated with 50 L3s each became infected i.p.; 92 adult worms were recovered from the positive animals. Four of 5 (80%) ferrets given subcutaneous inoculations of 50 L3s became infected; only 6 worms were recovered from these 4 animals. Inoculation of larvae via the i.p. or s.c. route greatly simplifies the infection procedure and produces more consistent results. A simple procedure is described, which permits rapid recovery of L3s to be used in the i.p. or s.c. inoculations.

Animals↗
PubMed1990

Distribution, behavior, and course of patency of Dracunculus insignis in experimentally infected ferrets.

From 106 ferrets experimentally infected with Dracunculus insignis, 273 female worms and 42 male worms were recovered. The percentage of female worms that mated, the location of all worms, and the rate of emergence of gravid females were recorded. Of 174 mature female worms recovered, only 11% had emerged before necropsy. Eighty-one percent of the male worms and 87% of all unmated (immature) females were found on the trunk of the animal or on the skin overlying it. Gravid female worms were found on the extremities (legs) 88% of the time. Almost one-third of gravid female worms were found on the left front leg. On 4 occasions, females were found in unusual locations: the tail, the cheek, the lumbar region of the spinal cord, and the peritoneal cavity associated with the omentum. The results showed that only a small percentage of mature female worms emerge, which suggests that infected persons harbor many more gravid female worms than indicated by reports of emergent worms. More than one-third of female worms were not mated, but it is likely that these immature females would be capable of further development. Furthermore, male worms have been observed to survive for up to 330 days, suggesting that male or unmated female worms may carry over from one transmission season to the next.

Animals↗
PubMed1989

Uptake and development of Wuchereria bancrofti in Culex quinquefasciatus that fed on Haitian carriers with different microfilaria densities.

In studies conducted between 1984 and 1986, the vector competency of Culex quinquefasciatus was assessed after bloodfeeding on 61 Haitian volunteers with different densities of Wuchereria bancrofti microfilariae (mf) and on 11 that were amicrofilaremic. Infected volunteers included persons previously given diethylcarbamazine citrate for 12 consecutive days and some that were untreated. Mosquitoes, derived from field-collected larvae, were released under bed nets and fed upon the volunteers while they slept. The mean mf uptake in mosquitoes that fed on 21 carriers with low to ultralow densities (1-28 mf/ml blood) was 0.2-4 mf/mosquito (mean = 1.7 mf). The observed infectivity rate of greater than 3,000 mosquitoes that fed on high (56-7,500 mf/ml blood; median = 525), low (11-49 mf/ml blood; median = 20), or ultralow (1-10 mf/ml blood; median = 3) density carriers was 4, 11, and 30 times higher, respectively, than the expected rate calculated from the estimated volume of the imbibed bloodmeal. These results indicate that "hidden" carriers (less than 50 mf/ml blood) may serve as a source of infection for mosquitoes, and support the increasing evidence that mosquitoes ingest more microfilariae than expected.

Animals↗
PubMed1989

Red Dracunculus medinensis.

Two instances of the emergence of a bright-red worm from humans in Pakistan are described. A 25-year-old man and a 26-year-old woman, unrelated and living in separate households, were observed in 1987 and 1988, respectively, to have emergent worms typical in size and location for Guinea worm disease, except for the color of the worms. The posterior end of 1 worm was recovered and appeared to be a female Dracunculus medinensis. Histologic sections provided insufficient information to determine the cause of the red color, although we could exclude blood as the cause.

Adult↗
PubMed1989

Heightened anti-filarial immune responsiveness in a Haitian pediatric population.

The immunological consequences of exposure to filarial infection were examined by cross-sectional serological studies. Serum samples from 121 pediatric patients (18 months-15 years of age) were analyzed in parallel with a panel of sera from adults residing in the same area of Haiti. Parasite antigen specific IgG and IgE levels were determined by ELISA. IgG levels in children were significantly elevated in humoral immunoreactivity to Brugia pahangi extracts compared to adults. In addition, anti-filarial IgG levels in amicrofilaremic children were significantly greater than in microfilaremic children. In contrast, IgG levels in adults were equivalent independent of microfilaremic status. Anti-filarial IgE levels in sera from both children and adults were low in comparison to that of a subject with tropical pulmonary eosinophilia and were unrelated to clinical status. No correlations were found between humoral responses and age, sex, or degree of parasitemia. Sera from amicrofilaremic children and, to a lesser extent, adults recognize more antigens, particularly those of high molecular weight (greater than 55 kDa), than sera from microfilaremic patients.

Adolescent↗
PubMed1989

Effectiveness of spaced doses of diethylcarbamazine citrate for the control of bancroftian filariasis.

Forty-seven Wuchereria bancrofti microfilaria carriers were treated once weekly for 12 weeks with 6 mg/kg DEC-C. Microfilaria densities ranged from 1 to 101 mf/20 cmm (MfD-50 of 9.75 mf/20 cmm) before treatment. Of 42 persons who completed treatment, 26 (62%) were microfilaria negative in 1-ml venous blood samples. Microfilaria densities in the 16 patients that remained positive ranged from 1 to 50 mf/ml (MfD-50 of 2.59 mf/ml). Weekly spaced doses of DEC-C resulted in a significant reduction in the number of microfilaria carriers posttreatment, and in the level of residual microfilaremia when compared to daily administration of the drug. Administration of spaced doses of DEC-C also resulted in better patient compliance with less dropout from the program. The reason DEC-C is more effective in spaced doses still remains unclear, but the role platelets or other cells may play in mediating the action of the drug may be linked to the administration schedule.

Adolescent↗
PubMed1989

Further evidence of a skewed distribution of microfilariae in capillary blood.

Reported are results for 23 Haitian patients with capillary Wuchereria bancrofti microfilaremias greater than 30 mf/20 cmm blood. In capillary blood, the number of microfilariae was 0.9 to 7.8 times greater than expected when compared with that in venous blood. When the values for venous blood and capillary blood from these high count patients were plotted, the simple linear regression y = a + bx (r2 = .36) and the exponential function y = aebx (r2 = .34) both represented the relationship. However, when values for high and low count patients were plotted, the power function y = axb (r2 = 0.82) best described the relationship between the number of microfilariae in venous and capillary blood.

Animals↗
PubMed1988

The effect of diethylcarbamazine treatment of Bancroftian filariasis on the immunological reactivity of microfilaraemic individuals.

Patent filarial infection has been correlated with a profound suppression of humoral and cellular responses to filarial antigens. In the present study, the filarial antigen-specific humoral and cellular reactivity of 30 Haitian subjects with patent Wuchereria bancrofti infection was monitored before and after treatment with diethylcarbamazine. Microfilarial density was reduced from a pre-treatment mean of 1778/ml to 9/ml, with residual microfilaraemias detectable in 10 subjects. Peripheral blood mononuclear cells from 18 of the 30 patients responded to an extract of Brugia pahangi before treatment, and this number increased to 25 after treatment. There was no significant change in the mean level of response to B. pahangi in patients who were responsive to filarial antigen before treatment; however, the mean responsiveness to B. pahangi of individuals who were classified as nonresponders before treatment was significantly increased following treatment. Cellular reactivity to purified protein derivative and geometric mean titres to soluble B. pahangi, measured by enzyme-linked immunosorbent assay, were unaffected by treatment. Similarly, most post-treatment sera did not recognize new B. pahangi bands on Western blots, compared to pre-treatment controls. These observations imply that the relationship between microfilariae and immunosuppression is complex.

Adolescent↗
PubMed1988

Dracunculus insignis: experimental infection in the ferret, Mustela putorius furo.

The laboratory study of dracunculiasis has suffered from the lack of a suitable, readily available animal model. We have been able to experimentally infect ferrets. Mustela putorius furo, with the North American dracunculid, Dracunculus insignis. Ferrets were inoculated with 75 to 100 infective larvae and were necropsied 90 to 240 days later. Guinea worms were recovered from 10 (56%) of 18 ferrets. A total of 44 worms were recovered, for an average of 4.4 worms per infected ferret. Gravid female worms were recovered as early as 128 days postinoculation. Thirteen (87%) of 15 gravid female worms were recovered from the extremities. Living male worms were recovered at 200 days of age, indicating that not all male worms die shortly after mating. First-stage larvae recovered from gravid females as early as 200 days of age were found to be infective to the copepod, Acanthocyclops vernalis. These observations suggest that the ferret is an excellent laboratory animal for dracunculiasis research.

Animals↗
PubMed1988

Bancroftian filariasis in Haiti: preliminary characterization of the immunological responsiveness of microfilaremic individuals.

Patent infections with the lymphatic filariae, Wuchereria bancrofti and Brugia malayi, are associated with suppressed in vitro cellular responsiveness to filarial antigens. In studies of bancroftian filariasis in Haiti, a significant number of microfilaremic individuals can be characterized as "responders" to filarial antigens. Cells from 37/74 untreated microfilaremic subjects responded to B. pahangi antigen (stimulation ratio greater than 2) as detected by in vitro blastogenesis. A comparison of responders to nonresponders revealed a significant difference in mean B. pahangi reactivity (15,822 vs. 4,538 cpm, P less than 0.001), but no significant differences with respect to age, microfilaremia, PPD or PHA reactivity, or B. pahangi-specific antibody levels. Subtle differences may exist between these groups with respect to recognition of specific antigens on Western blots.

Animals↗
PubMed1988

Persistence of microfilaremia in bancroftian filariasis after diethylcarbamazine citrate therapy.

Of 58 patients in Leogane, Haiti, infected with Wuchereria bancrofti and treated with diethylcarbamazine citrate (DEC-C) at 6 mg/kg per day for 12 days (= 72 mg/kg), 38 (66%) of 58 continued to harbor low numbers of circulating microfilariae (median microfilariae could be demonstrated in 7 (37%) of 19 patients, with a median microfilarial density of 8 mf/ml. Three patients who continued to have circulating microfilariae after two courses of DEC-C were treated a third time. Two (67%) of the three remained microfilaria positive, both with 1 mf/ml. The results of this study clearly indicate that a high percentage of persons infected with W. bancrofti and treated with one or multiple courses of DEC-C may continue to have circulating microfilariae after treatment. We suspect that these low-level reservoir carriers substantially contribute to the transmission of filariasis and may well account for the resurgence of infection levels following control efforts.

Animals↗
PubMed1988

Comparative densities of Wuchereria bancrofti microfilaria in paired samples of capillary and venous blood.

Concurrent finger-prick and venous blood samples were obtained from 43 patients infected with Wuchereria bancrofti. Microfilariae were counted in blood smears and on nuclepore filters. Based on the numbers of microfilariae in 20-microliters finger-prick samples, an expected (theoretical) number of microfilariae in venous samples was calculated. This expected value was compared to the actual number of microfilariae present in venous blood. The actual number of microfilariae present ranged from 0.7 to 30 times (median 3) less than expected. The exponential function y = 16.74e.17x, r2 = .69, where y = venous counts and x = capillary counts was found to accurately reflect the relationship between venous and capillary counts. Each unit (microfilaria) change in capillary blood would result in an expected 19% unit increase/decrease in venous blood. The results support strongly the theory that microfilariae are unevenly distributed in the blood system. The epidemiological implication is that persons with low or ultralow microfilaremia levels in venous blood may have a much greater pool of microfilaria available in capillaries. We believe that the present study explains, at least partially, why mosquitoes feeding on these kinds of microfilaria carriers (frequently) have a greater uptake fo microfilariae than expected.

Adolescent↗
PubMed1986

Loa loa: output of microfilariae in single pair infections.

The intent of the present study was to assess the production and release of microfilariae by a single female filaria, in an in vivo system. Experimental infections of Loa loa were established in baboons by implantation of juvenile worms, typically, one female and two or three males. Infected animals were bled weekly and the number of microfilariae counted. Microfilarial counts were converted to number of microfilariae per milliliter and then the total number of microfilariae present calculated for the total volume of blood. Weekly increases in microfilarial counts were calculated for each animal. During the primary wave of microfilariae, the average weekly increase ranged from 16,000 to 194,000 (ave. 74,000). This figure gave an average daily output of 10,000 microfilariae per female. During the secondary wave of microfilariae following splenectomy, the average weekly increase ranged from 83,000 to 270,000 (ave. 157,000), giving an average daily output of 22,000 microfilariae per female. It is postulated that this level of production occurs only during the early phase of infection and is markedly reduced after the microfilaremia plateaus. The results indicate that the shedding of microfilariae by the female worm does not occur necessarily on a daily or weekly basis, and that female worms do not shed uniform numbers of microfilariae over a given period of time.

Animals↗
PubMed1986

Longevity of microfilariae following removal of the adult worms.

The present study was undertaken to determine the longevity of a population of microfilariae in a natural host following the removal of the adult worms without drug intervention. Four squirrel monkeys previously infected with Dipetalonema gracile were allowed to develop stable microfilaremias. All adult worms were then removed surgically from the peritoneal cavity. Weekly microfilaria counts were made on each animal and the decline in microfilariae recorded. At the time of adult worm removal, microfilaremias ranged from 750 to 12,500 mf/ml. The observed decline in microfilaria densities was gradual, but steady, in all animals. Microfilariae persisted in 1-ml blood samples for 60, 62, 91, and 101 weeks following removal of adult worms. The results indicate clearly that in a naturally produced population, in a natural definitive host, microfilariae survive for 60 to 100 weeks. The gradual decrease in microfilarial densities would appear to be the result of the death of specific batches or broods of microfilariae. The microfilariae which persisted in the blood the longest undoubtedly represent those which were produced just prior to the removal of the adult worms. It is postulated that because of the long life-span of microfilariae, female worms are not called upon to produce a continual supply of microfilariae, nor is the need for mating as frequent as might be expected. Equally important, the number of microfilariae which the host is called upon to phagocytize is considerably smaller than previously suggested.

Animals↗
PubMed1986

Acanthocheilonema sabanicolae n. sp. (Filarioidea: Onchocercidae) from the savanna armadillo (Dasypus sabanicola) in Venezuela, with comments on the genus Acanthocheilonema.

A new species of Acanthocheilonema, Acanthocheilonema sabanicolae n. sp., is described from the subcutaneous tissues of the savanna armadillo (Dasypus sabanicola) in Venezuela. The adults (females 25-30.6 mm long by 61-78 micron wide; males 10.9-15.3 mm long by 42-44 micron wide) and the microfilariae (112-131 micron long by 3-5 micron wide) are the smallest within the genus. The microfilaria, a skin dweller, assumes a characteristic C-shaped curve, when fixed in 2% formalin, which serves to distinguish A. sabanicolae from others in the genus. Moreover, the spicules are notably smaller than any others in the Acanthocheilonema. Acanthocheilonema sabanicolae is the first species in this genus to be described from edentates, and, along with A. reconditum of dogs and A. pricei of opossums, is the third species of Acanthocheilonema to be reported from South America. Morphological features, vectors, and vertebrate hosts of the genus Acanthocheilonema are reviewed.

Animals↗
PubMed1986

The effect of repeated blood meals on the larval development of Dirofilaria corynodes in the fat body of Aedes aegypti.

The objective of the study was to determine whether blood meals taken by a vector subsequent to the infective one have any influence on the course of development of a filarial parasite in its tissue. The filaria Dirofilaria corynodes (von Linstow, 1899) was selected for study and the black-eye strain of Aedes aegypti served as the experimental vector. The microfilaria of D. corynodes develops to the infective stage in the fat bodies of the vector. Following an infective blood meal, mosquitoes were maintained on 10% sugar water alone (group A) or received supplementary blood meals i.e., an uninfected blood meal prior to the first larval molt followed by another after it (group B), an early blood meal (group C) or a late blood meal (group D). It was observed that additional blood meals after the infective one enhance the rate of larval development regardless of the timing of the feedings. An early blood meal, even if it is the only one, has a long-term significant effect on development. Repeated blood meals do not have an additive effect but tend to result in greater uniformity in larval size. A late blood meal also has a positive effect on development although the larval filariae do not grow or mature as rapidly as in the groups already mentioned. Larvae from mosquitoes fed on sugar water alone tended to develop at a slower rate and with less uniformity. It is concluded that infected mosquitoes taking one or more additional blood meals will yield a larger number of infective larvae in a shorter period of time.

Aedes↗