Robert C. Lowrie

Epidemiology of Wuchereria bancrofti in Leogane, Haiti

A survey for Wuchereria bancrofti in Leogane, Haiti, revealed that 140 of 421 individuals (33%) had a patent infection, of which 40% lived in the suburban outskirts of the city. The median microfilaria density was 19.1 per 20 mm3 of blood for suburban dwellers compared with only 8.8 for those living in the city. The vector, Culex quinquefasciatus (Say), breeds mostly in and around numerous rum distilleries, located exclusively around the periphery of the city, and this undoubtedly accounts for the higher prevalence and intensity of infection among suburban dwellers.

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.

DEVELOPMENT OF DIPETALONEMA GRACILE AND D. CAUDISPINA TO THE INFECTIVE STAGE IN CULICOIDES HOLLENSIS

The microfilariae of 2 species of Dipetalonema (i.e., D. gracile and D. caudispina), common parasites of South American monkeys, develop to the third (infective) stage in the biting midge, Culicoides hollensis. Development of both species occurs in the abdominal fat body; D. gracile requires 13 days and D. caudispina 9 days. Despite similarities in the patterns of development of both species, the third-stage larvae of each is morphologically distinct.

DEVELOPMENT OF DIPETALONEMA GRACILE IN THE SQUIRREL MONKEY (SAIMIRI SCIUREUS), WITH NOTES ON ITS BIOLOGY

Infective larvae of Dipetalonema gracile, which had developed in Culicoides hollensis, were inoculated into 4 laboratory-born squirrel monkeys, Saimiri sciureus. Weekly blood sampling revealed the mean prepatent period to be 297 days. All 4 monkeys developed patent infections in which peak microfilaremias were reached 13 to 18 wk after patency. Two laparotomies, performed at 27 and 64 wk, were conducted to evaluate pathological involvement and, at that later time, to recover adult parasites. Slight capsular fibrosis was observed on the spleen of 2 of the animals but fibrous adhesions were absent. Microfilaremias in the 4 monkeys ranged from 15 to 250 mf/20 mm3 of blood and the number of adult parasites recovered varied from 7 to 13. However, the level of microfilaremia did not correlate directly to the number of adult parasites recovered.

Differential humoral and cellular immunoreactivity to saline-and detergent-extracted filarial antigens

The immunoreactivity to saline- and detergent-extracted filarial antigens of 31 Haitian subjects exposed to or infected with Wuchereria bancrofti was analysed. Cellular reactivity, monitored by blastogenesis in vitro, was significantly greater to a soluble extract of Brugia pahangi than to a detergent-extracted antigenic preparation. In contrast, serum antibody levels against the detergent extract were significantly higher. These differences were consistently observed in symptomatic, microfilaraemic, and asymptomatic/amicrofilaraemic groups of patients. These patterns of immunoreactivity may reflect intrinsic differences between the 2 antigenic preparations in terms of composition or their mode of presentation to the host immune system.

Laboratory studies on Mansonella marmosetae in the squirrel monkey, Saimiri sciureus.

gether, and it is more probable that they are exposed equally to parasite propagules. Given the mixed-age, mixed-sex groups in which bobwhites live during the winter, differences in parasite burdens may be rare. We are grateful for the assistance of personnel of the Southeastern Cooperative Wildlife Disease Study, The University of Georgia, which was provided under the Federal Aid in Wildlife Restoration Act (50 Stat. 917) and through contract Nos. 14-16-0009-82-500, 14-16-0004-83004, and 14-16-0004-84-005, Fish and Wildlife Service, U.S. Department of the Interior. We appreciate the field assistance of J. Atkinson and B. Mueller (Tall Timbers Research Station) and the technical assistance of S. Forster and J. Liberatos (Florida State University). Dr. R. Short (FSU) provided laboratory space and Colorado State University provided computer time. This study was funded by NSF BSR-8210218 to J. Moore, D. Simberloff, and R. Short and NSF BSR-8452076 to J. Moore.

Blastogenic responses, interleukin‐2 production and interleukin‐2 receptor expression on CD4+ and CD8+ lymphocytes in rhesus monkeys experimentally inoculated with Loa loa

To better understand cellular responses in loiasis infection, in vitro blastogenesis of peripheral blood mononuclear cells (PBMC) to filarial antigen was assessed in 12 Loa loa‐inoculated rhesus monkeys over a two‐year period. Cellular reactivity to antigen was observed between 10–35 weeks postinoculation (WPI), but had declined by week 50. The roles of interleukin‐2 (IL‐2) and IL‐2 receptor (IL‐2R) expression on CD4+ and CD8+ T cells in regulating the response to antigen were examined during the initial (57 WPI) and late (92 WPI) time points of the observed diminished reactivity to antigen. The levels of IL‐2 in antigen cultures at both time points were not significantly different from those in unstimulated cultures. Also, exogenous IL‐2 partially reversed the PBMC response to antigen. The percentages of CD4+ and CD8+ T cells expressing IL‐2R in antigen cultures at 57 WPI were not different from those of control animals. Likewise at 92 WPI, the percentage of CD4+ T cells expressing IL‐2R in antigen cultures, were not increased above those of control animals. In contrast, the percentage of CD8+ T cells expressing IL‐2R in antigen cultures were significantly increased above those of control animals (P < 0.0001), coinciding with an increase in CD8+ T cell numbers in these cultures. The data show that factors besides IL‐2, and probably an imbalance in the percentages of CD4+ and CD8+ T cells bearing IL‐2R in antigen cultures, may contribute to the diminished reactivity to antigen in L. loa‐inoculated rhesus monkeys.

DEVELOPMENT OF TETRAPETALONEMA LLEWELLYNI TO THE INFECTIVE STAGE IN CULICOIDES HOLLENSIS

The vector requirements and course of larval development for tetrapetalonema llewellyni Price, 1962, a common filaria of raccoons in Louisiana, are described for the first time. Development (from microfilaria to infective stage) took place in the thoracic muscles of the biting midge, Culicoides hollensis (Melander and Brues, 1902) Foote and Pratt, 1954, and required 9 days under laboratory conditions. The findings of this study suggest that species of Culicoides may serve as natural vectors of T. llewellyni.

Development of Tetrapetalonema marmosetae to the infective stage in Culicoides hollensis and C. furens.

Development of the microfilaria of Tetrapetalonema marmosetae to the infective stage is described in 2 species of biting midges, Culicoides furens and C. hollensis. Development takes place in the thoracic muscles where the microfilaria requires 8 days to reach the third, or infective, stage. These observations suggest that species of Culicoides are the probable natural vectors of T. marmosetae in enzootic areas and that possibly a wide range of midges will serve as suitable vectors for the parasite in the laboratory. The elucidation of the life cycle, the first for a filaria from a neotropical primate, opens the way for the maintenance of this parasite in the laboratory and provides another useful tool for experimental study.