Trypanosoma cruzi genetic diversity: Something new for something known about Chagas disease manifestations, serodiagnosis and drug sensitivity.

A 42-year-old woman presents after donating blood and receiving a report that she is positive for Chagas' disease. Chagas' disease is caused by a parasite and is endemic in many parts of Latin America.

Antitrypanosomal Therapy for Chronic Chagas' Disease

Do radically dissimilar Trypanosoma cruzi strains (zymodemes) cause Venezuelan and Brazilian forms of Chagas' disease?

The reservoir capacity of domestic cats and dogs for Trypanosoma cruzi infection and the host-feeding patterns of domestic Triatoma infestans were assessed longitudinally in 2 infested rural villages in north-western Argentina. A total of 86 dogs and 38 cats was repeatedly examined for T. cruzi infection by serology and/or xenodiagnosis. The composite prevalence of infection in dogs (60%), but not in cats, increased significantly with age and with the domiciliary density of infected T. infestans. Dogs and cats had similarly high forces of infection, prevalence of infectious hosts (41–42%), and infectiousness to bugs at a wide range of infected bug densities. The infectiousness to bugs of seropositive dogs declined significantly with increasing dog age and was highly aggregated. Individual dog infectiousness to bugs was significantly autocorrelated over time. Domestic T. infestans fed on dogs showed higher infection prevalence (49%) than those fed on cats (39%), humans (38%) or chickens (29%) among 1085 bugs examined. The basic reproduction number of T. cruzi in dogs was at least 8·2. Both cats and dogs are epidemiologically important sources of infection for bugs and householders, dogs nearly 3 times more than cats.

/pdf/domestic-dogs-and-cats-as-sources-of-trypanosoma-cruzi-48rurkouje.pdf

Domestic dogs and cats as sources of Trypanosoma cruzi infection in rural northwestern Argentina

Starch-gel electrophoresis of 38 enzymes was attempted with extracts of Trypanosoma cruzi culture forms. 18 of the enzymes that gave discrete electrophoretic bands were selected for routine characterization of T. cruzi stocks; the enzymes were: aspartate aminotransferase (E.C. 2.6.1.1, ASAT); alanine aminotransferase (E.C.2.6.1.2, ALAT); phosphoglucomutase (E.C.2.7.5.1, PGM); glucosephosphate isomerase (E.C.5.3.1.9, GPI); malate dehydrogenase (oxaloacetate decarboxylating) (NADP+) (E.C.1.1.1.40, ME); glucose 6-phosphate dehydrogenase (E.C.1. 1.1.49, G6PD); malate dehydrogenase (E.C.1.1.1.37, MDH); aconitate hydratase (E.C.4.2.1.3, ACON); isocitrate dehydrogenase (NADP+) (E.C.1.1.1.42, ICD); alcohol dehydrogenase (NADP+) (E.C.1.1.1.2, ADH); lactate dehydrogenase (E.C.1.1.1.27, LDH); aminopeptidase (cytosol) (E.C.3.4.11.1, PEP); pyruvate kinase (E.C.2.7.1.40, PK); phosphoglycerate kinase (E.C.2.7.2.3, PGK); enolase (E.C.4.2.1.11, ENO); hexokinase (E.C.2.7.1.1, HK); mannosephosphate isomerase (E.C.5.3.1.8, MPI); and glutamate dehydrogenase (E.C. 1.4.1.2, GD). ADH (NADP+) in the genus Trypanosoma, and PGK, MPI and ENO, in T. cruzi, were apparently demonstrated for the first time. Between six and 18 enzymes were used to characterize more than 250 T. cruzi stocks, newly isolated from a wide range of sources in northern and central Brazil. All stocks were identified as belonging to T. cruzi zymodemes 1, 2 or 3, as originally defined—that is, by combination of electrophoretic patterns of ASAT, ALAT, PGM, GPI, ME and G6PD. The composite range of results with all enzymes confirmed the presence of three principal T. cruzi zymodemes, but some enzymic characters overlapped between zymodemes and others suggested subgroups within individual zymodemes. Seven (MDH, ACON, LDH, PK, PGK, ENO, HK) of the 18 enzymes did not distinguish the three zymodemes; five (ASAT, PGM, GPI, ICD, PEP) distinguished all three zymodemes; 10 (ASAT, ALAT, PGM, GPI, ME, G6PD, ICD, ADH, PEP, GD) distinguished zymodemes 1 and 2, of which seven plus MPI and eight plus MPI separated zymodemes 1 from 3 and 2 from 3 respectively. T. cruzi stocks were taken from a small area of the natural species distribution; the full range of enzymic characters within the species T. cruzi is expected to be far more complex. The epidemiological distribution of the zymodemes continued to accord with local transmission cycles and supported the hypothesis that distinct T. cruzi strains might be responsible for the enigmatic distribution of chronic Chagas's disease. Some of the difficulties in the empirical selection of new electrophoretic methods and the interpretation of results were presented, and the present and prospective significance of T. cruzi enzymic characters was discussed. Until the stability and genetic basis of T. cruzi enzymic characters are better understood it is recommended that isoenzymic profiles be confirmed routinely, both before and after stocks are used experimentally, as representative of a given zymodeme. A multiple biochemical approach to T. cruzi strain identification is recommended, using characters suitable for a numerical taxonomy.

Further enzymic characters of Trypanosoma cruzi and their evaluation for strain identification.

Culture forms of 104 stocks of Trypanosoma cruzi isolated in different regions of the State of Bahia were compared by electrophoresis of six enzymes. The three distinct combinations of isoenzyme patterns seen were designated ZI, Z2 and Z3. In an area of endemic Chagas's disease in eastern Bahia, T. cruzi Z1 was associated with sylvatic mammals and sylvatic triatomines, whereas T. cruzi Z2 was associated with a separate domestic cycleof transmission. T. cruzi Z1 was also found in sylvatic triatomines from other parts of the State. In contrast, in an area of the Sao Francisco Valley region of western Bahia, both T. cruzi Z1 and Z2 were isolated from man, domestic animals, and peridomestic rats. T. cruzi Z3 was isolated from an armadillo and from Panstrongylus geniculatus, a triatomine commonly found in armadillo burrows. Both T. cruzi Z1 and Z2 appeared to be pathogenic in man: T. cruzi Z1 was isolated from patients with acute Chagas's disease and from a single patient with chronic cardiac manifestations. T. cruzi Z2 was isolated from some asymptomatic individuals but was also associated with acute disease and chronic cardiac and digestive syndromes.

https://www.arca.fiocruz.br/bitstream/icict/13831/2/Barrett%20TV%20Epidemiological%20aspects.....pdf

Epidemiological aspects of three Trypanosoma cruzi zymodemes in Bahia State, Brazil.

The relationship between parasitemia, seroreactivity to Trypanosoma cruzi, and electrocardiographic abnormalities was studied in 115 individuals from a rural community in northeast Brazil where Chagas' disease is endemic. Vector control measures were introduced, and after 3 years 106 of the original participants were located and re-examined. Serum antibodies to T. cruzi were measured by complement fixation and indirect fluorescent antibody tests and parasitemia by xenodiagnosis and blood cultures. On both examinations more seropositive children than seropositive adults showed parasitemia, and parasitemia was more likely to persist over the 3-year period in younger individuals. Electrocardiographic (ECG) abnormalities were seen more frequently in seropositive individuals without parasitemia. However, ECG abnormalities, as expected, were more prevalent in older individuals and therefore no specific inverse relationship between ECG findings and parasitemia could be shown. The decreased prevalence of infection noted in younger individuals following the introduction of vector control measures indicates that this approach limited transmission.

J A Almeida de Souza

Papers

Epidemiological aspects of three Trypanosoma cruzi zymodemes in Bahia State, Brazil.

A three-year follow-up study of infection with Trypanosoma cruzi and electrocardiographic abnormalities in a rural community in northeast Brazil.