Annals of Tropical Medicine & Parasitology
ISSN: 0003-4983 (Print) 1364-8594 (Online) Journal homepage: http://www.tandfonline.com/loi/ypgh19
Prevalence of Entamoeba histolytica and other intestinal parasites in a community from Maracaibo, Venezuela L. Chacin-Bonilla, E. Bonilla, A. M. Parra, J. Estevez, L. M. Morales & H. Suarez To cite this article: L. Chacin-Bonilla, E. Bonilla, A. M. Parra, J. Estevez, L. M. Morales & H. Suarez (1992) Prevalence of Entamoeba histolytica and other intestinal parasites in a community from Maracaibo, Venezuela, Annals of Tropical Medicine & Parasitology, 86:4, 373-380, DOI: 10.1080/00034983.1992.11812680 To link to this article: http://dx.doi.org/10.1080/00034983.1992.11812680
Published online: 15 Nov 2016.
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Citing articles: 5 View citing articles
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Date: 25 August 2017, At: 02:09
Annals of Tropical Medicine and Parasitology, Vol. 86, No.4, 373-380 (1992)
Downloaded by [Australian Catholic University] at 02:09 25 August 2017
Prevalence of Entamoeba histolytica and other intestinal parasites in a community from Maracaibo, Venezuela BY L. CHACIN-BONILLA, E. BONILLA, A. M. PARRA, J. ESTEVEZ, L. M. MORALES AND H. SUAREZ Instituto de Investigaciones Clinicas, Apartado 1151, Universidad del Zulia, Maracaibo, Venezuela
Received 15 October, 1991, Accepted 18 February 1992
The prevalences of Entamoeba histolytica and other intestinal parasites were assessed in a suburban community of Maracaibo, Venezuela, by examination of a stool specimen from each of 342 individuals, using ironhaematoxylin stained faecal smears and formalin-ether concentration. The overall parasitic infection rate was 80·4%, and 65·8% of the population had multiple infections. The overall amoebic infection rate, which was highest in female adults, averaged 39· 7%. The E. histolytica infection rate was 8· 7% and most of those infected were passing cysts. Entamoeba polecki was observed in two samples. Amongst the protozoa, Entamoeba coli was observed most frequently (24·8%) and Giardia Iamblia was the predominant pathogen (13·0%). Trichuris trichiura (71·9%) and Ascaris lumbricoides (54%) were the most common parasites, particularly in schoolchildren. The high rates of parasitic and multiple infections reflect the low socio-economic status of the community studied.
Most data on the prevalences of intestinal parasitic infections in Venezuela are biased, because they come from studies on selected individuals, such as the hospitalized and others seeking medical attention. True prevalences, which must be derived from unselected populations, are generally unknown. Entamoeba histolytica infection rates in the general population are thus difficult to obtain, particularly as amoebic infections are misdiagnosed in Venezuela, as in other parts of the world (Elsdon Dew, 1968; Walsh, 1986), because routine laboratory diagnosis is based on direct faecal examination and Entamoeba hartmanni and E. histolytica are not differentiated. Extensive parasitological studies, undertaken in rural and suburban areas throughout the country in 1947-19 59, revealed high prevalances of infection with the helminths Trichuris trichiura (77%), Ascaris lumbricoides (59%), hookworm (52%), Strongyloides stercora/is 0003-4983/92/040373 + 08 $08.00/0
(0·9%) and Taenia spp. (1·3%). Since then, there have been very few reports on parasite prevalences in Venezuelan communities. Recently, to obtain a more accurate picture of the present epidemiology of intestinal parasites, studies have been undertaken in Zulia State, north-western Venezuela, on several communities of low socio-economic status (ChacinBonilla and Dikdan, 1981; Chacin-Bonilla eta!., 1984a,b, 1987, 1990a). These investigations have avoided the bias inherent in most selected populations and have been based on the examination, using iron-haematoxylin staining and formalin-ether concentration, of a single stool sample from each individual. They have contributed to the documentation of the pattern of intestinal parasitization in Venezuela, indicating that 54-92% of the study populations had intestinal parasites of at least one species and 49-89% had multiple parasitoses. The © 1992 Liverpool School of Tropical Medicine
Downloaded by [Australian Catholic University] at 02:09 25 August 2017
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most prevalent parasite in these surveys was T. trichiura (27-83%), followed, in the helminths, by A. /umbricoides (20-75%), hookworm (1-6%), S. stercora/is (1-2·5%), H. nana (1-6%) and Taenia spp. (0·0-0·3%). Amongst the protozoa, Entamoeba coli was the most prevalent amoeba (18-28%) and Giardia Iamblia the predominant pathogen (11-18%), followed by E. histo/ytica (3-9%). The prevalence of E. hartmanni varied from 1-6·5%. The aims of the present study were to investigate the prevalence of infection with E. histolytica and with other intestinal parasites in a community in the suburbs of Maracaibo City and to speculate on certain epidemiological factors that could play a role in the parasite's dissemination in the environment. MATERIALS AND METHODS The Study Community The study was conducted in San Luis, a suburban village in the coastal lowlands on the shores of Lake Maracaibo, south of Maracaibo City, the capital ofZulia State, in north-western Venezuela. The area has a tropical and arid climate, with mean annual temperature, relative humidity and rainfall of 28°C, 78% and 747 mm, respectively. The village has a population of about 1790 and has been subjected to several multidisciplinary studies, as one of the village families has the world's highest concentration of Huntington's chorea (Wexler eta/., 1984). It has low socio-economic and sanitary standards. Some streets are unasphalted and others have many pot-holes which fill with water during the rainy season. Overflowing sewage and piles of rubbish are frequently observed. Most (65%) of the housing units have indoor plumbing and 35% have piped water. Although 56% of the population have adequate sewerage, 4% have latrines, 20% defecate in the open, particularly on the lake shore and near their houses, and 20% have a channel system whereby the faeces are washed into the lake, even though this is used for bathing. The majority of the houses have one or two dormitories for six or more occupants; overcrowding and close contact between villagers,
and with the cats, dogs, poultry and pigs of the village, are very common. The population tends to behave as one large family, but with frequent intermarriages. Thirty-eight per cent of the household heads are unemployed and 40% are illiterate. Survey Methods The survey was undertaken in April-July 1989. Each of the housing units to be included in the study was determined by random sampling and then visited to gain the co-operation of the family. An adult member of each household was interviewed and the names, ages, sexes and any gastro-intestinal complaints of the members of the household recorded. Single stool samples were collected in the morning from each of 342 individuals in the study households, taken to the laboratory and processed within an hour. Faecal smears were made for immediate fixation and staining with iron-haematoxylin(TompkinsandMiller, 1947) and a portion of each specimen was concentrated by the formalin-ether method (Ritchie, 1948) prior to examination. Data Analysis The amoebic prevalence rate (APR), which has been suggested as an index of amoebic infection (Brooke et al., 1955), was determined; an individual with one or more of the most common amoebae, E. histolytica, E. harmanni, E. coli and E. nana) was counted as a single positive. For statistical analysis, Chi-squared and Fisher's exact tests were used. The study population was classified into five age groups: zero to six years (preschool children), seven to 12 years (schoolchildren), 13-18 years (adolescents), 19-45 years (adults) and > 45 years (adults).
RESULTS Over 80% of stool samples contained at least one species of parasite (Table 1). Eleven species of protozoa and five of helminths were identified. Trichuris trichiura (71·9%) was the most common parasite, followed by A. lumbricoides (54%). Amongst the protozoa, E. coli (24·8%) was the most frequent and G. Iamblia (13%) the
ENTAMOEBA IN A VENEZUELAN COMMUNITY
375
TABLE 1 Parasite prevalences detected in stool samples from San Luis
Downloaded by [Australian Catholic University] at 02:09 25 August 2017
Positive specimens
Amoebic prevalence rate Entamoeba histolytica Entamoeba hartmanni Entamoeba polecki Entamoeba coli Endolimax nana Iodamoeba butschlii Dientamoeba fragilis Giardia Iamblia Trichomonas hominis Chilomastix mesnili Balantidium coli Trichuris trichiura Ascaris lumbricoides Hookworm Strongyloides stercora/is Hymenolepis nana Parasitic infection rate
No.
%
136 30 16 2 85 68 15 3 45 14 9 2 246 185 28 29 35 275
39·7 8·7 4·6 0·5 24·8 19·8 4·4 0·8 13-1 4·0 2·6 0·5 71·9 54·0 8·1 8·4 10·2 80·4
TABLE2 Frequency(%) ofsingle and multiple infections
Age group (years)
No. of species
0--6 N=63
7-12 N=30
13-18 N=29
19-45 N=116
>45 N=37
All ages N=275
One Two Three Four Five Six Seven Eight
28·5 34-9 19·0 7·9 6·3 0 1·6 1·6
16·7 26·7 30·0 13·3 6·6 6·6 0 0
27·5 34-4 17-2 13·8 3-4 0 0 3-4
38·7 39·6 14·7 2·6 2·6 0 1·7 0
48·6 29·7 13·5 2·7 0 5·4 0 0
34·2 35·3 17-4 6·2 3-6
predominant pathogen. Entamoeba polecki and Balantidium coli, common parasites of pigs, were each observed in two cases. The APR was high (39·7%). Unidentified nematode larvae were found in two cases and Enterobius vermicularis
1-4 1·0 0·7
eggs were found in samples from six children (data not shown in tables). Table 2 indicates the high prevalence of multiple infections; infection with a single parasite species was only observed in 34· 2% of
Downloaded by [Australian Catholic University] at 02:09 25 August 2017
376
CHACIN-BONILLA ET AL.
individuals. Although the greatest number of species carried by an individual was eight, most (P
ISSN: 0003-4983 (Print) 1364-8594 (Online) Journal homepage: http://www.tandfonline.com/loi/ypgh19
Prevalence of Entamoeba histolytica and other intestinal parasites in a community from Maracaibo, Venezuela L. Chacin-Bonilla, E. Bonilla, A. M. Parra, J. Estevez, L. M. Morales & H. Suarez To cite this article: L. Chacin-Bonilla, E. Bonilla, A. M. Parra, J. Estevez, L. M. Morales & H. Suarez (1992) Prevalence of Entamoeba histolytica and other intestinal parasites in a community from Maracaibo, Venezuela, Annals of Tropical Medicine & Parasitology, 86:4, 373-380, DOI: 10.1080/00034983.1992.11812680 To link to this article: http://dx.doi.org/10.1080/00034983.1992.11812680
Published online: 15 Nov 2016.
Submit your article to this journal
View related articles
Citing articles: 5 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ypgh19 Download by: [Australian Catholic University]
Date: 25 August 2017, At: 02:09
Annals of Tropical Medicine and Parasitology, Vol. 86, No.4, 373-380 (1992)
Downloaded by [Australian Catholic University] at 02:09 25 August 2017
Prevalence of Entamoeba histolytica and other intestinal parasites in a community from Maracaibo, Venezuela BY L. CHACIN-BONILLA, E. BONILLA, A. M. PARRA, J. ESTEVEZ, L. M. MORALES AND H. SUAREZ Instituto de Investigaciones Clinicas, Apartado 1151, Universidad del Zulia, Maracaibo, Venezuela
Received 15 October, 1991, Accepted 18 February 1992
The prevalences of Entamoeba histolytica and other intestinal parasites were assessed in a suburban community of Maracaibo, Venezuela, by examination of a stool specimen from each of 342 individuals, using ironhaematoxylin stained faecal smears and formalin-ether concentration. The overall parasitic infection rate was 80·4%, and 65·8% of the population had multiple infections. The overall amoebic infection rate, which was highest in female adults, averaged 39· 7%. The E. histolytica infection rate was 8· 7% and most of those infected were passing cysts. Entamoeba polecki was observed in two samples. Amongst the protozoa, Entamoeba coli was observed most frequently (24·8%) and Giardia Iamblia was the predominant pathogen (13·0%). Trichuris trichiura (71·9%) and Ascaris lumbricoides (54%) were the most common parasites, particularly in schoolchildren. The high rates of parasitic and multiple infections reflect the low socio-economic status of the community studied.
Most data on the prevalences of intestinal parasitic infections in Venezuela are biased, because they come from studies on selected individuals, such as the hospitalized and others seeking medical attention. True prevalences, which must be derived from unselected populations, are generally unknown. Entamoeba histolytica infection rates in the general population are thus difficult to obtain, particularly as amoebic infections are misdiagnosed in Venezuela, as in other parts of the world (Elsdon Dew, 1968; Walsh, 1986), because routine laboratory diagnosis is based on direct faecal examination and Entamoeba hartmanni and E. histolytica are not differentiated. Extensive parasitological studies, undertaken in rural and suburban areas throughout the country in 1947-19 59, revealed high prevalances of infection with the helminths Trichuris trichiura (77%), Ascaris lumbricoides (59%), hookworm (52%), Strongyloides stercora/is 0003-4983/92/040373 + 08 $08.00/0
(0·9%) and Taenia spp. (1·3%). Since then, there have been very few reports on parasite prevalences in Venezuelan communities. Recently, to obtain a more accurate picture of the present epidemiology of intestinal parasites, studies have been undertaken in Zulia State, north-western Venezuela, on several communities of low socio-economic status (ChacinBonilla and Dikdan, 1981; Chacin-Bonilla eta!., 1984a,b, 1987, 1990a). These investigations have avoided the bias inherent in most selected populations and have been based on the examination, using iron-haematoxylin staining and formalin-ether concentration, of a single stool sample from each individual. They have contributed to the documentation of the pattern of intestinal parasitization in Venezuela, indicating that 54-92% of the study populations had intestinal parasites of at least one species and 49-89% had multiple parasitoses. The © 1992 Liverpool School of Tropical Medicine
Downloaded by [Australian Catholic University] at 02:09 25 August 2017
374
CHACIN-BONILLA ET AL.
most prevalent parasite in these surveys was T. trichiura (27-83%), followed, in the helminths, by A. /umbricoides (20-75%), hookworm (1-6%), S. stercora/is (1-2·5%), H. nana (1-6%) and Taenia spp. (0·0-0·3%). Amongst the protozoa, Entamoeba coli was the most prevalent amoeba (18-28%) and Giardia Iamblia the predominant pathogen (11-18%), followed by E. histo/ytica (3-9%). The prevalence of E. hartmanni varied from 1-6·5%. The aims of the present study were to investigate the prevalence of infection with E. histolytica and with other intestinal parasites in a community in the suburbs of Maracaibo City and to speculate on certain epidemiological factors that could play a role in the parasite's dissemination in the environment. MATERIALS AND METHODS The Study Community The study was conducted in San Luis, a suburban village in the coastal lowlands on the shores of Lake Maracaibo, south of Maracaibo City, the capital ofZulia State, in north-western Venezuela. The area has a tropical and arid climate, with mean annual temperature, relative humidity and rainfall of 28°C, 78% and 747 mm, respectively. The village has a population of about 1790 and has been subjected to several multidisciplinary studies, as one of the village families has the world's highest concentration of Huntington's chorea (Wexler eta/., 1984). It has low socio-economic and sanitary standards. Some streets are unasphalted and others have many pot-holes which fill with water during the rainy season. Overflowing sewage and piles of rubbish are frequently observed. Most (65%) of the housing units have indoor plumbing and 35% have piped water. Although 56% of the population have adequate sewerage, 4% have latrines, 20% defecate in the open, particularly on the lake shore and near their houses, and 20% have a channel system whereby the faeces are washed into the lake, even though this is used for bathing. The majority of the houses have one or two dormitories for six or more occupants; overcrowding and close contact between villagers,
and with the cats, dogs, poultry and pigs of the village, are very common. The population tends to behave as one large family, but with frequent intermarriages. Thirty-eight per cent of the household heads are unemployed and 40% are illiterate. Survey Methods The survey was undertaken in April-July 1989. Each of the housing units to be included in the study was determined by random sampling and then visited to gain the co-operation of the family. An adult member of each household was interviewed and the names, ages, sexes and any gastro-intestinal complaints of the members of the household recorded. Single stool samples were collected in the morning from each of 342 individuals in the study households, taken to the laboratory and processed within an hour. Faecal smears were made for immediate fixation and staining with iron-haematoxylin(TompkinsandMiller, 1947) and a portion of each specimen was concentrated by the formalin-ether method (Ritchie, 1948) prior to examination. Data Analysis The amoebic prevalence rate (APR), which has been suggested as an index of amoebic infection (Brooke et al., 1955), was determined; an individual with one or more of the most common amoebae, E. histolytica, E. harmanni, E. coli and E. nana) was counted as a single positive. For statistical analysis, Chi-squared and Fisher's exact tests were used. The study population was classified into five age groups: zero to six years (preschool children), seven to 12 years (schoolchildren), 13-18 years (adolescents), 19-45 years (adults) and > 45 years (adults).
RESULTS Over 80% of stool samples contained at least one species of parasite (Table 1). Eleven species of protozoa and five of helminths were identified. Trichuris trichiura (71·9%) was the most common parasite, followed by A. lumbricoides (54%). Amongst the protozoa, E. coli (24·8%) was the most frequent and G. Iamblia (13%) the
ENTAMOEBA IN A VENEZUELAN COMMUNITY
375
TABLE 1 Parasite prevalences detected in stool samples from San Luis
Downloaded by [Australian Catholic University] at 02:09 25 August 2017
Positive specimens
Amoebic prevalence rate Entamoeba histolytica Entamoeba hartmanni Entamoeba polecki Entamoeba coli Endolimax nana Iodamoeba butschlii Dientamoeba fragilis Giardia Iamblia Trichomonas hominis Chilomastix mesnili Balantidium coli Trichuris trichiura Ascaris lumbricoides Hookworm Strongyloides stercora/is Hymenolepis nana Parasitic infection rate
No.
%
136 30 16 2 85 68 15 3 45 14 9 2 246 185 28 29 35 275
39·7 8·7 4·6 0·5 24·8 19·8 4·4 0·8 13-1 4·0 2·6 0·5 71·9 54·0 8·1 8·4 10·2 80·4
TABLE2 Frequency(%) ofsingle and multiple infections
Age group (years)
No. of species
0--6 N=63
7-12 N=30
13-18 N=29
19-45 N=116
>45 N=37
All ages N=275
One Two Three Four Five Six Seven Eight
28·5 34-9 19·0 7·9 6·3 0 1·6 1·6
16·7 26·7 30·0 13·3 6·6 6·6 0 0
27·5 34-4 17-2 13·8 3-4 0 0 3-4
38·7 39·6 14·7 2·6 2·6 0 1·7 0
48·6 29·7 13·5 2·7 0 5·4 0 0
34·2 35·3 17-4 6·2 3-6
predominant pathogen. Entamoeba polecki and Balantidium coli, common parasites of pigs, were each observed in two cases. The APR was high (39·7%). Unidentified nematode larvae were found in two cases and Enterobius vermicularis
1-4 1·0 0·7
eggs were found in samples from six children (data not shown in tables). Table 2 indicates the high prevalence of multiple infections; infection with a single parasite species was only observed in 34· 2% of
Downloaded by [Australian Catholic University] at 02:09 25 August 2017
376
CHACIN-BONILLA ET AL.
individuals. Although the greatest number of species carried by an individual was eight, most (P
