A study of Cryptosporidium parvum genotypes and population structure.

Genetic evidence for the occurrence of two Cryptosporidium parvum subgroups is presented. This evidence is based on restriction fragment length polymorphism analysis of several independent loci. Sequence analysis of the beta-tubulin intron revealed additional polymorphism. The stability of the genetic profiles following passage of C. parvum isolates between different hosts was investigated.

Multilocus genotypic analysis of Cryptosporidium parvum isolates from different hosts and geographical origins.

The genetic analysis of oocysts recovered from the stools of humans and animals infected with Cryptosporidium parvum has consistently shown the existence of two distinct genotypes. One of the genotypes is found exclusively in some human infections, whereas the other genotype is found in human as well as in animal infections. On the basis of these observations and the results of published epidemiological studies with single polymorphic markers, the existence of two separate transmission cycles has been postulated, one exclusively anthroponotic and the other involving both animals and humans. To test this hypothesis, C. parvum isolates of different geographic and host origins were analyzed by using unlinked genetic polymorphisms. A total of 28 isolates originating from Europe, North and South America, and Australia were examined. Isolates clustered into two groups, one comprising both human and animal isolates and the other comprising isolates only of human origin. The absence of recombinant genotypes is consistent with two reproductively isolated populations within the species C. parvum.

RNA polymerase activity is associated with viral particles isolated from Leishmania braziliensis subsp. guyanensis.

Viral particles purified from species of the protozoan parasite Leishmania braziliensis subsp. guyanensis by centrifugation in CsCl gradients were examined for the presence of viral polymerase. We demonstrated that RNA-dependent RNA polymerase is associated with viral particles. Viral transcription was studied in vitro with pulse-chase experiments and by assaying the RNase sensitivity of the viral transcripts. Viral polymerase synthesized full-length transcripts within 1 h. Double-strained, genome-length, and single-stranded RNAs were produced in this system. The nature of the RNA extracted from virions was also tested by RNase protection assays; both single-stranded and double-stranded RNAs were found.

Epidemiology of Chagas' disease in northern Chile: isozyme profiles of Trypanosoma cruzi from domestic and sylvatic transmission cycles and their association with cardiopathy.

Trypanosoma cruzi was isolated from 98 patients, 59 Triatoma infestans, 51 Triatoma spinolai, and 1 Octodon degus from northern Chile. With few exceptions, stocks originating from domestic hosts were classified, based on their isozyme profile, as principal zymodeme (Z)2, while sylvatic stocks from T. spinolai and the rodent O. degus showed Z1 profiles. These results indicate the existence of separate domestic and sylvatic transmission cycles. Clinical data and T. cruzi isozyme profiles from 107 chronic Chagas' disease patients showed no association between infecting T. cruzi zymodeme and the prevalence of chagasic cardiopathy. However, the age distributions of two groups of patients carrying different zymodemes were significantly different.

Isozyme profiles of Trypanosoma cruzi stocks from Colombia and Ecuador.

A total of 74 of 82 domestic Rhodnius prolixus from the same locality in eastern Colombia were found to be infected with Trypanosoma cruzi or T. rangeli. One of three domestic Triatoma dimidiata from Ecuador also showed T. cruzi infection. A total of 59 T. cruzi stocks from these and five other localities in Colombia were isolated from man, marsupials and triatomine bugs. Cellulose-acetate electrophoresis of nine or ten enzymes characterized all T. cruzi stocks as zymodeme 1 (reference clone Silvio X10/1). Differences in electrophoretic patterns between the newly isolated stocks and the zymodeme 1 standard were seen with the enzymes G6PD and HK. These results are in agreement with the previously described geographical distribution of T. cruzi zymodemes. Stocks were isolated from both low and high altitudes and there was no evidence of adaptative significance of T. cruzi enzyme polymorphism.

Isozyme heterogeneity and numerical taxonomy of Trypanosoma cruzi stocks from Chile.

Fifty-three stocks of Trypanosoma cruzi were isolated in Chile, 13 from patients, 32 from the domestic triatomine vector Triatoma infestans, and 8 from the silvatic and peridomestic vector T. spinolai. The majority of isolates from triatomine bugs were made by the direct culture of infected faeces. The 53 stocks and a single clone were characterized by a combination of starch-gel and cellulose acetate enzyme electrophoresis. Three groups of T. cruzi stocks were apparent from either simple visual comparisons of isozyme profiles or numerical taxonomy. The groups were designated Chilean zymodeme (Z) 1, which was similar to Brazilian Z1, Chilean Z2a, similar to Brazilian Z2 and Chilean Z2b, similar to Bolivian Z2 and with prominent heterozygous isozyme profiles. Chilean Z1 was isolated only from T. spinolai colonizing farm walls inhabited by the rodent Octodon degus. Chilean Z2a and Z2b were both isolated from domestic T. infestans T. infestans and man, in some cases within the same household. Hardy-Weinberg equilibria were not found amongst a group of 22 stocks from a single locality and deviations from theoretical Hardy-Weinberg distributions were compatible with the absence of genetic exchange in the sampled population of T. cruzi.