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The host selection pattern and infection rates of Panstrongylus megistus in an area of eastern Brazil
290 Experiments
T H I R T E E N T H S E M I N A R ON TRYPANOSOMIASIS
w i t h s e r o l o g i c a l m e t h o d s o n the d i f f e r e n t i a l d i a g n o s i s p a n o s o m i a s i s in cattle i n A f r i c a s o u t h o f the S a h a r a
of try-
R. S C H I N D L E R
Bernhard-Nocht Institut, Hamburg In an earlier publication (SCHINDLER, 1972) I reported that antibodies produced by cattle after an infection with Trypanosoma brucei, T. congolense or T. vivax showed a strong reaction when homologous trypanosome species were used as an antigen and that the reaction was weak or absent with heterologous species. In the investigation I used the indirect method of immunofluorescence and the complement-fixation test only. Later investigations with the haemagglutination test showed that after an infection with T. congolense cattle produce heterophilic antibodies of high titre which disturb the specific reaction greatly. Experiments to differentiate the trypanosome species with the direct agglutination test had inconclusive results. Investigations with culture forms of T. theileri and sera with antibodies against T. brucei, T. vivax and T. congolense had negative results. T h e I g M concentration in the plasma of 2 of our experimental cattle was investigated by Mrs. Oelerich. 1 animal was infected with T. brucei and showed no obvious symptoms; 1 animal was infected with T. congolense and died from the infection. After the T. congolense infection there was an early and marked rise in the concentration of IgM. After the T. brucei infection the concentration of this globulin increased at a late stage after the infection. In both cases specific serologic antibodies could be demonstrated much earlier.
D o m e s t i c r i s k f a c t o r - - a n a t t e m p t to a s s e s s r i s k o f i n f e c t i o n w i t h Trypanosoma cruz/ in houses in Brazil D. M. M I N T E R , E. M I N T E R - G O E D B L O E D , P. D. M A R S D E N , M. A. M I L E S AND V. M A C E D O
Fundafao Gonfalo Moniz and London School of Hygiene and Tropical Medicine, Chagas's Disease Research Unit, Salvador, Bahia, Brazil A method is proposed to estimate the risk of the infection of man with Trypanosoma cruzi in houses infested with triatomine bugs. 2 parameters are estimated, the number of bugs caught per man hour of search (apparent density--assumed to be proportional to the bug population density) and the percentage T. cruzi-infection rate in the bugs caught. T h e product of these 2 parameters divided by 100 is termed the Domestic Risk Factor. T h e factor has been estimated for 30 houses in Silo Felipe, Bahia, Brazil and the values have been compared with evidence of infection in the inhabitants of the houses. T h e latter was estimated by "scoring" each individual for evidence of infection--5 points for a positive xenodiagnosis, 3 points for a positive fluorescent antibody test and 2 points for each significant E C G change. From these scores a mean infection score per caput was calculated. Domestic Risk Factors varied from 0 to 35 and mean infection scores from 0 to 7.7. A general correspondence was found between the 2 estimates, suggesting that Domestic Risk Factor may be a useful epidemiological concept. An evaluation has commenced of the predictive value of the Domestic Risk Factor, as a measure by which to classify household bug infestation as constituting a risk to the future infection of susceptible individuals. It is likely that this concept will be limited to areas where the triatomine vector is essentially a static, domiciliated species; such is the case with Panstrongylus megistus in the Sao Felipe area. This study is the result of collaboration between the Fundaq~o Gonqalo Moniz, the Nucleo de Pesquisas da Bahia and the Chagas's Disease Research Team of the London School of Hygiene and Tropical Medicine (supported by the Wellcome Trust).
T H I R T E E N T H S E M I N A R ON TRYPANOSOMIASIS
w i t h s e r o l o g i c a l m e t h o d s o n the d i f f e r e n t i a l d i a g n o s i s p a n o s o m i a s i s in cattle i n A f r i c a s o u t h o f the S a h a r a
of try-
R. S C H I N D L E R
Bernhard-Nocht Institut, Hamburg In an earlier publication (SCHINDLER, 1972) I reported that antibodies produced by cattle after an infection with Trypanosoma brucei, T. congolense or T. vivax showed a strong reaction when homologous trypanosome species were used as an antigen and that the reaction was weak or absent with heterologous species. In the investigation I used the indirect method of immunofluorescence and the complement-fixation test only. Later investigations with the haemagglutination test showed that after an infection with T. congolense cattle produce heterophilic antibodies of high titre which disturb the specific reaction greatly. Experiments to differentiate the trypanosome species with the direct agglutination test had inconclusive results. Investigations with culture forms of T. theileri and sera with antibodies against T. brucei, T. vivax and T. congolense had negative results. T h e I g M concentration in the plasma of 2 of our experimental cattle was investigated by Mrs. Oelerich. 1 animal was infected with T. brucei and showed no obvious symptoms; 1 animal was infected with T. congolense and died from the infection. After the T. congolense infection there was an early and marked rise in the concentration of IgM. After the T. brucei infection the concentration of this globulin increased at a late stage after the infection. In both cases specific serologic antibodies could be demonstrated much earlier.
D o m e s t i c r i s k f a c t o r - - a n a t t e m p t to a s s e s s r i s k o f i n f e c t i o n w i t h Trypanosoma cruz/ in houses in Brazil D. M. M I N T E R , E. M I N T E R - G O E D B L O E D , P. D. M A R S D E N , M. A. M I L E S AND V. M A C E D O
Fundafao Gonfalo Moniz and London School of Hygiene and Tropical Medicine, Chagas's Disease Research Unit, Salvador, Bahia, Brazil A method is proposed to estimate the risk of the infection of man with Trypanosoma cruzi in houses infested with triatomine bugs. 2 parameters are estimated, the number of bugs caught per man hour of search (apparent density--assumed to be proportional to the bug population density) and the percentage T. cruzi-infection rate in the bugs caught. T h e product of these 2 parameters divided by 100 is termed the Domestic Risk Factor. T h e factor has been estimated for 30 houses in Silo Felipe, Bahia, Brazil and the values have been compared with evidence of infection in the inhabitants of the houses. T h e latter was estimated by "scoring" each individual for evidence of infection--5 points for a positive xenodiagnosis, 3 points for a positive fluorescent antibody test and 2 points for each significant E C G change. From these scores a mean infection score per caput was calculated. Domestic Risk Factors varied from 0 to 35 and mean infection scores from 0 to 7.7. A general correspondence was found between the 2 estimates, suggesting that Domestic Risk Factor may be a useful epidemiological concept. An evaluation has commenced of the predictive value of the Domestic Risk Factor, as a measure by which to classify household bug infestation as constituting a risk to the future infection of susceptible individuals. It is likely that this concept will be limited to areas where the triatomine vector is essentially a static, domiciliated species; such is the case with Panstrongylus megistus in the Sao Felipe area. This study is the result of collaboration between the Fundaq~o Gonqalo Moniz, the Nucleo de Pesquisas da Bahia and the Chagas's Disease Research Team of the London School of Hygiene and Tropical Medicine (supported by the Wellcome Trust).