Endemic human fasciolosis in the Bolivian Altiplano

Abstract

Fasciolosis, caused by trematodes of the genus Fasciola, is an emerging disease of humans. One of the highest levels of human fasciolosis hepatica is found amongst the indigenous Aymaran people of the Northern Bolivian Altiplano. A meta-analysis of epidemiological surveys from 38 communities in the region demonstrates that fasciolosis has been endemic in the region since at least 1984 and is a zoonosis of rural communities. Human and bovine fasciolosis is associated with the communities lying in the plain from Lake Titicaca to La Paz, predominantly in the Los Andes province. In Los Andes incidences of up to 67% of population cohorts were found, and prevalence is age-related with the highest infection rate in children aged 8-11 years.

Fig. 1

Cattle and human infection in the Bolivian Altiplano. Communities: (1) Guaqui; (2) Viacha; (3) Calasaya; (4) Cutusuma; (5) Chijipata Alta; (6) Huacullani; (7) Quiripujo; (8) Caleria; (9) Coropata; (10) Batallas; (11) Tambillo; (12) Pucarani; (13) El Alta; (14) Chasquipampa; (15) Tuaca; (16) Santiago De Huata; (17) Coromata Baja; (18) Copancara, (19) Achacachi; (20) Huatajata; (21) Cuyahuani; (22) Kharapata; (23) Pantini; (24) Oketiti; (25) Iquiaca; (26) Ancocagua; (27) Achocalla; (28) Tuni; (29) Kajchiri; (30) Ticuyo; (31) Aygachi; (32) Belen Yayes; (33) Cohana; (34) Lacaya Baja; (35) Yanarico; (36) Chambi Grande; (37) Causaya; (38) Kallutaca; Data were obtained for a total of 7908 individuals from 38 communities in the Northern Bolivian Altiplano from four provinces (Los Andes, Ingavi, Omasuyos, and Murillo) around the La Paz region covering the period 1984–1998 [, , –20]. Within these provinces, 25 communities from Los Andes, four communities from Ingavi, five from Murillo, and six communities from Omasuyos were sampled. Infection rates are represented by symbols: Open circles <10% human infection; small closed circles 10–25%; medium closed circles >25–40%; large closed circles >40%. The presence or absence of infection in cattle was obtained from 4750 cattle in 86 differing communities. Cattle infection is represented by triangles (open triangles, no infection; closed triangles, infection). Areas with gradients >3° are diagonally shaded. The scale bar represents 10 km.

Fig. 2

The effect of province, community size and community on infection. CHAID (chi-squared automated interaction detection) was used to separate the population from the Northern Bolivian Altiplano into subgroups based on the proportion of infected and non-infected individuals. The predictor variables were province, community size (<2000, ⩾2000) and community. Numbering of the communities is consistent with that for Figure 1.

Fig. 3

The effect of community and age on infection. Data was available for the age structure of the samples (10-year age bands) for a subset of the village communities from the Los Andes province with CHAID used to assess the effect of community and age grouping on infection rate. Numbering of the communities is consistent with that for Figure 1.

Fig. 4

Age profile of community infection rate in the communities of Calasaya, Cutusuma and Chijipata Alta. For analysis of the affect of age on infection rates, a subset of the data from three communities of Los Andes province with high infection rates was used. These were Calasaya (89 individuals), Cutusuma (150 individuals), and Chijipata Alta (29 individuals) (268 individuals in total).