A mallophaga, Trinoton anserinum, as a cyclodevelopmental vector for a heartworm parasite of waterfowl.

The biting louse Trinoton anserinum serves as the intermediate host in the life cycle of the filarial heartworm, Sarconema eurycerca. Microfilariae, second-, and third-stage larvae were dissected from 39 of 89 lice infesting whistling swans, Cygnus columbianus columbianus, in North America and mute swans, Cygnus olor, in the Black Sea, U.S.S.R. Infective third-stage larvae obtained from lice collected from heartworm-parasitized whistling swans were injected subcutaneously into each of two hand-reared, nonparasitized mute swan cygnets. Both of these birds developed heartworm infections, one becoming microfilaremic at 14 weeks. The results of this study provide conclusive evidence that a mallophagan serves as a natural cyclodevelopmental vector of a filarial parasite.

Strongyloides ratti infections in rats. I. Immunopathology.

The elimination of adult parasites from the intestines of rats after a first and second infection of Strongyloides ratti was studied. Expulsion after a second infection was anamnestic, indication that the response is immunologic. Intestinal mast cell responses accompanied damage and expulsion of worms, the secondary mast cell response being more rapid but less intense that the first. Antithymocyte serum suppressed expulsion as well as both the intestinal mast cell and circulating eosinophil responses to primary infection.

Strongyloides ratti infections in rats. II. Effects of cortisone treatment.

Cortisone (5 mg daily subcutaneously) suppressed both primary and secondary immune explusion of Strongyloides ratti, and reduced the intestinal mast cell response, but did not induce hyperinfection in rats. Cortisone-treated animals expelled primary worm burdens without complication about 2 wk after steroid treatment. A model for gastrointestinal hypersensitivity syndromes in discussed.

Morphogenesis of larval Onchocerca volvulus in the Panamanian black fly, Simulium quadrivittatum.

Simulium quadrivittatum Loew (Diptera: Simuliidae), a man-biting black fly, was shown, for the first time, to be capable of supporting development of Onchocerca volvulus Leuckart (Nematoda: Filarioidea) from microfilariae to third-stage (infective) larvae. The black flies were collected in Chiriqui Province, Panama and transported alive to Guatemala, where they were allowed to feed on a human subject infected with O. volvulus. Samples of these flies were dissected over an 11-day period to assess morphogenesis of the parasite. Vigorously motile microfilariae were recovered from the mid-gut during the first 24 hours postfeeding; second-stage larvae were found in the thoracic musculature on day 4; and fully developed third-stage larvae were obtained from the cephalic capsule by day 10. This rate of larval development is similar to that observed in Guatemalan S. ochraceum. Onchocerciasis is not known to occur in Panama. The results of the present study direct attention to a potential public health hazard there and possibly elsewhere in Central America.

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.

Evaluation of the slide-latex agglutination and intradermal (Casoni) tests for echinococcosis.

Fifty-one patients with surgically proven hydatid disease were examined with the intradermal (ID) (Casoni) and latex-agglutination (LA) tests. Before surgery, results of the former test were 80.4% positive and of the latter were 82.3%. For 105 persons who were diagnosed free of hydatid cysts by surgical, clinical and serological observations, 6.7% were positive with the ID test and 4.8% with the LA test. The close agreement between results obtained with the LA and ID tests in this selected group of patients suggests that the LA test merits further evaluation as a diagnostic tool.

The cryopreservation and in vitro cultivation of larval Onchocerca volvulus.

A system developed in our laboratory for the in vitro cultivation of larval Onchocerca volvulus is being employed in a series of morphogenetic, physiologic, chemotherapeutic and immunologic investigations of this parasite. Because of the need for a large and readily available supply of living worms for this work, cryogenic techniques are being used for the long-term preservation of larval parasites collected in various endemic areas of Guatemala, C.A. To date, microfilariae have survived frozen storage in human cutaneous tissues (excised nodules and skin snips) for as long as 504 days, and viable larvae, in all stages of development have been recovered from the black fly vectors (Simulium ochraceum and S. metallicum) kept frozen for 396 days. That cryopreservation does not appear to affect these parasites adversely is indicated by the fact that microfilariae derived from frozen tissues do not differ from those obtained from fresh tissues on the basis of: 1) numbers and vigor of emergent microfilariae; 2) survival and morphogenesis of microfilariae during cultivation in vitro for 24 days; 3) glucose utilization during 72 hours of incubation; and 4) their incorporation of 3H-amino acids as determined after 18 hours of incubation. Details of methodology for cryopreservation and in vitro cultivation, together with resultant data, are presented herein.

Histopathology of hepatic and pulmonary granulomata experimentally induced with eggs of Schistosoma mansoni.

Hepatic granulomata were experimentally induced in previously unexposed white mice, albino rats and golden hamsters by injecting viable exogenous eggs of Schistosoma mansoni via the mesenterico-portal system. Histopathologic studies of livers of these animals showed that the lesions were similar to those in infections resulting form exposure to cercariae as occurs naturally in Mansonian schistosomiasis. Comparable observations made of the lungs of animals that had received egg injections via their tail veins, showed striking differences with respect to timing of the occurrence of various histopathologic stages, mean size of granulomata, cellular composition and pathologic manifestations.

The occurrence and distribution of 5-hydroxytryptamine in Hymenolepis diminuta and H. nana.

The presence of 5-HT in Hymenolepis diminuta and Hymenolepis nana was detected by 2 biochemical methods and as yellow fluorescence in a histochemical method. In H. diminuta, 5-HT was found in a concentration of about 1.2 micron/g; this amount did not vary significantly in worms aged 6 to 18 days or more or in various regions of the worm. In H. nana, 5-HT was found in a concentration of about 1.8 micron/g. It was histochemically localized in H. diminuta and H. nana in a pattern similar to that of acetylcholinesterase previously described in these 2 cestodes, and it may be the opposing neuro-transmitter to acetylcholine. The lack of 5-HT in the vestigial rostellum of H. diminuta may be correlated with loss of function of this organ.

Pathology of larval Eustrongylides in the rabbit.

Three fishermen from Maryland who swallowed live bait-minnows developed severe abdominal pain within 24 hr; 2 required abdominal surgery. Larvae of the nematode Eustrongylides sp. were found in the peritoneal cavity of both (Guerin et al., 1982). In the current study, the lesions produced by Eustrongylides larvae were investigated in New Zealand white rabbits. None of these exhibited any signs of clinical illness; however, postmortem examination within 24 hr of inoculation revealed that larvae had migrated through the walls of the esophagus and stomach and viable larvae were recovered from the pleural and peritoneal cavities as well as from gastric contents. Necropsies performed at different intervals of time postinoculation showed that the migrating larvae had produced multi-focal peritonitis and multiple granulomata in the liver.

Aerobic and anaerobic carbohydrate metabolism and egg production of Schistosoma mansoni in vitro.

When S. mansoni adults were cultured in vitro for 12 days in a diphasic medium, their gross morphology, motor activity, frequency of sexual pairings, rates of glucose utilization and of lactic acid production were the same in the presence (90% N2/5% O2/5% CO2) or absence (95% N2/5% CO2) of oxygen. Therefore, no Pasteur effect, nor any reduction in lactic acid formation, was demonstrable under aerobic conditions. While aerobic conditions did not affect the rate of glycolysis, they had a marked effect on egg production. In the presence of oxygen, the rate of egg-laying reached a maximum between days 4 and 6. The average number of viable eggs produced per worm pair during this period was 118 (Sx equals 2.2), which is within the overall range (68 to 248) recorded by others for this same strain in vivo. Conversely, under anaerobic conditions in vitro, virtually no eggs were laid. It remains to be determined whether oxidative metabolism actually is required for energy to produce eggs, or whether some reaction yielding no ATP is essential for completion of their developmental process, such as tanning of the eggshall brought about by the oxidation of some phenolic compounds.

Granuloma formation around exogenous eggs of Schistosoma mansoni and Schistosoma japonicum in mice.

Hepatic granulomata which were qualitatively and quantitatively similar to those seen in infections established with cercariae were induced by surgical injection of exogenous eggs of Schistosoma mansoni and Schistosoma japonicum via the mesenteric veins of previously unexposed albino mice. Thereafter, their comparative histopathologic studies were made. The maximum mean sizes of granulomata were attained on Day 32 with viable eggs of these parasite species. Although S. mansoni eggs produced significantly larger lesions (368.4 +/- 21.5 microns) than eggs of S. japonicum (205.8 +/- 18.6 microns) at the peak period, the difference in the mean granulomal size showed no correlation with either the time of onset or the severity of pathologic changes produced. Thus, eggs of S. japonicum with smaller granulomata, evoked pathologic changes which were earlier in onset and more severe than those produced by the same quantity of S. mansoni eggs. Since the most obvious variables (the quantity of eggs, the sequence of their arrival in the liver, the timing of observation, and the strain of experimental animals) were controlled, it was concluded that the most severe and fatal effects produced by eggs of S. japonicum, as previously suggested, are largely due to differences in the cytotoxic and antigenic peculiarities of this species.