Commercial coconut palm as an ecotope of Chagas disease vectors in north-eastern Venezuela.

BACKGROUND & OBJECTIVE: There are few reports of Coccus nucifera (Palmae) infestation by triatomines (Hemiptera, Reduviidae, Triatominae), vectors of Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae), the causal agent of American Trypanosomiasis. The aim of this study was to determine if this palm is an appropriate ecotope for Rhodnius prolixus and Triatoma maculata, the main vectors in Venezuela. METHODS: Dry and green leaves, humid debris, interfoliaceus meshes and bracts from C. nucifera from north-eastern Venezuela were examined for the presence of triatomines. Samples of the intestinal content of vectors, macerated in isotonic saline solution and haemolymph were examined microscopically for the presence of Trypanosoma spp. The parasites were isolated and characterized using biological parameters and PCR. Triatomine blood meal sources were determined using ELISA. RESULTS: A total of 14 palms were examined in which viable eggs of both species of vectors were found in 13 palms (92.85%). A total of 242 R. prolixus and 144 T. maculata adults were collected, of which 98% of R. prolixus and 70% of T. maculata individuals were infected by T. cruzi (TcI genotype) and 13% of R. prolixus individuals showed a mixed infection with T. rangeli, the other American trypanosome. ELISA testing for possible triatomine blood-meal sources revealed that these vectors are essentially eurytrophic and zoophilic, although R. prolixus also eventually used human blood as a nourishment source. INTERPRETATION & CONCLUSION: The results obtained suggest that C. nucifera is an appropriate vegetal niche for these triatomine species in Venezuela. The presence of this commercial palm may represent a useful environmental bioindicator of risk for Chagas disease.

Experimental transmission of Trypanosoma cruzi through the genitalia of albino mice.

Trypanosoma cruzi is usually transmitted by contact with the excreta of infected Triatominae; among non-vectorial infections, direct transmission through coitus has been proposed. We investigated this possibility by instilling, through the external meatus of the vagina and the penis of previously anesthetized NMRI albino mice, blood of mice infected with strains isolated from Didelphis marsupialis (opossum, strain CO57), Rattus rattus (rat, strain CO22) and human (strain EP). Some animals were allowed to copulate the same day of the instillation. In other experiments, the strains were inoculated in the scrotum. To determine the effect of immunosuppression, some mice were treated with cyclophosphamide 30 days post-instillation. Controls were instilled orally and ocularly. Vaginal instillation with strain CO22 produced systemic infection with tropism to the heart, skeletal muscle, skin, duodenum, pancreas, ovary and sternum. Scrotal inoculation with strain EP likewise invaded liver, spleen, lung, lymph nodes and urogenital organs; while strain CO57 invaded skeletal and cardiac muscle, pancreas, testis, and vas deferens. Penile infection with strain CO22 was detected by xenodiagnosis. Immunosuppression did not increase parasitemia of vaginally infected mice or controls. Mating did not produce infection. Our results show that contact of blood trypomastigotes of T. cruzi with genital mucosa can produce blood and tissue infections. These results are discussed in relation to reports of frequent experimental tropism of T. cruzi toward urogenital organs.

Synanthropic rodent reservoirs of Trypanosoma (Schizotrypanum) cruzi in the valley of Caracas, Venezuela.

Direct blood examination and xenodiagnosis of 47 synanthropic rodents (Rattus rattus, R. norvegicus, Mus musculus) captured in the valley of Caracas, Venezuela, revealed trypanosomal infections in 12 R. rattus, 10 with T. lewisi and 2 with T. cruzi. Of the latter the course of parasitemia, the pleomorphism of the bloodstream trypomastigotes, tissue in naturally and experimentally infected rats and mice, host mortality, morphology of fecal parasites in Rhodnius prolixus used for xenodiagnosis, and infectivity of the bug feces for NMRI mice, were all characteristic of Trypanosoma (Schizotrypanum) cruzi. One rat, with a patent parasitemia, had numerous nests of amastigotes in cardiac muscle and moderate parasitism of the smooth muscle of the duodenum and of skeletal muscle. Mice inoculated with fecal flagellates from the bugs had moderate tissue tropism in the same organs and also in the colon and pancreas. The possible role of R. rattus in the establishment of foci of Chagas' disease in Caracas is discussed.

Trypanosoma cruzi in the anal glands of urban opossums. I- isolation and experimental infections

Opossums (Didelphis marsupialis) captured in intensely urbanized areas of the city of Caracas, Venezuela, were found infected with Trypanosoma cruzi. The developmental cycle of trypomastigote-epimastigote-metacyclic infective trypomastigote, usually occurring in the intestine of the triatomine vector, was taking place in the anal odoriferous glands of the opossums. Material from the glands, inoculated in young, healthy opossums and white mice by different routes, subcutaneously, intraperitoneally, orally, and into the eye, induced T. cruzi infections in all animals. Parasitemia, invasion of cardiac and skeletal muscle, and intracellular multiplication of amastigotes were observed. Inoculation of metacyclics from anal glands, cultured in LIT medium, gave equivalent results. All opossums survived: all mice died. Excreta of opossums may thus transmit Chagas' disease by contamination, even in urban areas where insect vectors are not present.

Trypanosoma cruzi in the anal glands of urban opossums. I--Isolation and experimental infections.

Opossums (Didelphis marsupialis) captured in intensely urbanized areas of the city of Caracas, Venezuela, were found infected with Trypanosoma cruzi. The developmental cycle of trypomastigote-epimastigote-metacyclic infective trypomastigote, usually occurring in the intestine of the triatomine vector, was taking place in the anal odoriferous glands of the opossums. Material from the glands, inoculated in young, healthy opossums and white mice by different routes, subcutaneously, intraperitoneally, orally, and into the eye, induced T. cruzi infections in all animals. Parasitemia, invasion of cardiac and skeletal muscle, and intracellular multiplication of amastigotes were observed. Inoculation of metacyclics from anal glands, cultured in LIT medium, gave equivalent results. All opossums survived; all mice died. Excreta of opossums may thus transmit Chagas' disease by contamination, even in urban areas where insect vectors are not present.

Trypanosoma (Schizotrypanum) cruzi: histopathology in mice infected with strains isolated from Didelphis marsupialis from the valley of Caracas (Venezuela).

The histopathological alterations produced in NMRI strain mice by isolates of Trypanosoma cruzi from Didelphis marsupialis captured near human dwellings in the valley of Caracas, Venezuela are described. The donor opossums showed pseudocysts and amastigotes and trypomastigotes only in the heart muscle, and few areas of discrete inflammations and lysis of some muscle cells. Mice were parasitized in the heart, skeletal muscle, jejunum, colon, liver, lung, urinary bladder, penis, seminal vesicle, prostate, pancreas, and brain. All the isolates produced histiolymphocytic inflammation, severe in cardiac and skeletal muscle, and light in the smooth muscle of the intestine and urinary bladder; certain of the isolates produced destruction of muscle fibers. These findings, together with the morphology and behavior reported in previous papers, suggest that the isolates from this mammal reservoir and from the local vector (Panstrongylus geniculatus) belong to the same type. The possible venereal transmission through the parasitosis of the urogenital system is discussed. The necessity for characterization of strains of the parasite that have been isolated from areas of intense urbanization, where the ecological changes have reduced the number of host species, is emphasized; such studies may help to clarify the extreme heterogeneity of T. cruzi and the parasitoses it induces.

Population genetics of Trypanosoma cruzi and Trypanosoma rangeli: taxonomical and epidemiological purpose.

A genetic analysis of a set of Trypanosoma cruzi and Trypanosoma rangeli stocks was performed by two combined approaches, namely multilocus enzyme electrophoresis (MLEE) and labeling by DNA probes. A considerable genetic variability was evidenced within each of the two species. Since the upper level of resolution of the isoenzyme method was reached, it was impossible to draw any definite discrimination between the two species by usual clustering methods. Nevertheless, two markers appeared as species-specific, namely the malic enzyme, and a probe that hybridizes highly-repeated sequences of T. cruzi.

Didelphis marsupialis: a primary reservoir of Trypanosoma cruzi in urban areas of Caracas, Venezuela.

Direct blood examination and xenodiagnosis of 45 sylvatic, peridomestic or domestic mammals from the Caracas valley, Venezuela, revealed trypanosome infection in six of the 24 opossums, Didelphis marsupialis, collected in urban areas. Isolates were successfully made of trypanosomes from four of the opossums, using the parasites which developed in Rhodnius prolixus fed on the infected opossums to infect NMRI mice. The prepatent period, course of parasitaemia, morphology of bloodstream trypomastigotes, tissue tropism of parasites in the opossums and/or mice, host mortality, morphology of parasites in the bugs, and infectivity to mice of parasites in the faeces of infected bugs, were all characteristic of Trypanosoma (Schizotrypanum) cruzi. In mice, the parasites showed marked myotropism; the heart, skeletal muscle and the smooth muscle of the urinary bladder, penis, prostate, seminal vesicle, lung, stomach, jejunum and colon were frequently invaded, and pseudocyts were also occasionally found in the liver, brain and pancreas. The significance of the invasion of the genito-urinary structures as a possible alternative parasite transmission route is discussed. The possible role of D. marsupialis, as a primary reservoir of T. cruzi, in the establishment of foci of Chagas' disease in Caracas and other Latin American cities, is emphasized.

Trypanosoma rangeli (Tejera, 1920): observations upon pleomorphism

Metatrypomastigotes of Trypanosoma rangeli Tejera, 1920, harvested from LIT medium, were inoculated i.p. or s.c. into 6, 16, and 26g NMRI mice, these representing increasing degrees of immunological maturity. In all cases, similar pleomorphic patterns were observed. Four morphobiometrically differentiable types of trypanosome were encountered in an overlapping temporal sequence. These observations, taken in comparison with those on pleomorphism in this and other species of Trypanosoma by other workers, are consistent with the hypothesis that the pleomorphic types represent the natural development of the parasite, rather than the result of the immune response of the mammal host. Small, slender trypanosomes prevalent at the onset of the parasitemia either reinvade the tissue cells for relatively limited subsequent generations of tissue reproduction, or else differentiate toward the forms that are only capable of colonizing the insect vector

Trypanosoma rangeli (Tejera, 1920): observations upon pleomorphism.

Meta-trypomastigotes of Trypanosoma rangeli Tejera, 1920, harvested from LIT medium, were inoculated i.p. or s.c. into 6, 16, and 26 g NMRI mice, these representing increasing degrees of immunological maturity. In all cases, similar pleomorphic patterns were observed. Four morphobiometrically differentiable types of trypanosome were encountered in an overlapping temporal sequence. These observations, taken in comparison with those on pleomorphism in this and other species of Trypanosoma by other workers, are consistent with the hypothesis that the pleomorphic types represent the natural development of the parasite, rather than the result of the immune response of the mammal host. Small, slender trypanosomes prevalent at the onset of the parasitemia either reinvade the tissue cells for relatively limited subsequent generations of tissue reproduction, or else differentiate toward the forms that are only capable of colonizing the insect vector.

Urban Trypanosoma (Schizotrypanum) cruzi: pathology in white mice of isolates from Panstrongylus geniculatus.

The histopathological alterations produced in white mice (NMRI strain) by isolates of Trypanosoma (Schizotrypanum) cruzi from Panstrongylus geniculatus captured in dwellings of the city of Caracas, Venezuela are reported. The heart, skeletal muscle, liver, spleen, duodenum, colon, lung, and brain were parasitized by all the isolates. All showed strong myotropism, with elevated virulence and severe histopathological alterations in the cardiac and skeletal muscle, and in the smooth muscle of the duodenum, colon, and lung; parasitization of the mononuclear phagocytic system was discrete. These results, in addition to the morphobiological characters reported in a previous paper, suggest that the isolates in question belong to the same type of parasite. The possible causes of this observation are discussed in the light of the heterogeneity of T. cruzi. The epidemiological significance of the existence of these parasite forms in the urban areas of Caracas is emphasized.

Trypanosoma (Herpetosoma) rangeli Tejera, 1920: study of the effects of the parasite on the vector.

For evaluation of the possible pathogenicity of Trypanosoma (Herpetosoma) rangeli Tejera, 1920 to the triatomid vector, first-stage nymphs of laboratory-bred insects were engorged upon albino mice showing average parasitemias of 2 x 10(6) and 2 x 10(5) trypanosomes/ml blood. The vector strains were: Rhodnius prolixus ("New" strain), Triatoma pallidipennis, and Triatoma vitticeps. An "Old" strain of R. prolixus (maintained 30 years in the laboratory) was also employed to check the effects of laboratory breeding. Other lots of nymphs of the same vector strains were fed on healthy mice as controls. T. rangeli produced intense infections in the gut and hemolymph of all the vector tested, with later differentiation in the salivary glands to metatrypomastigotes that could be transmitted by the bite of the insect and establish infections in healthy mice. No statistically significant differences whatever between infected and control bugs were found for degree of engorgement, percentage or cause of mortality, molting time, oviposition/female, hatching time, percentage of hatching, or duration of life cycle. The possible role of experimental methodology in producing pathology in infected insects, and the epidemiological significance of a strain of T. rangeli non-pathogenic to the vector are discussed.