Fasciola hepatica Infection Risk for Adult Household Members Living with Children with Fascioliasis in Cusco, Peru

Abstract.

Fasciola hepatica is highly prevalent in the highlands of Peru. School-age children have the greatest risk of infection. Mass treatment of at-risk populations has been proposed to control the infection and prevent complications. However, the decreasing effectiveness of triclabendazole raises concerns regarding this strategy. Previous studies reported aggregation of Fasciola infection among family members. This study aimed to determine the risk of fascioliasis among household members living with Fasciola-infected children identified through school-based testing. We conducted a cross-sectional study including adult members of households where children with and without fascioliasis were identified. Demographic, epidemiological, and socioeconomic information was collected. One blood sample was drawn to test for Fasciola antibodies, and three stool samples were collected for microscopy for Fasciola ova. We tested 326 adults from 213 households. Of these adult subjects, chronic fascioliasis (24 of 326, 7.4%) was the most common helminth infection. Thirty-nine subjects (12.7%) tested positive for Fasciola antibodies. Combining microscopy and serum antibody tests, 13.2% (43 of 326) had evidence of Fasciola infection. One third (104 of 326, 31.9%) of the participants lived with at least one child infected with Fasciola hepatica. Adults with fascioliasis were four times more likely to live with an infected child. Poverty and diet were associated with increased risk of Fasciola infection. Adults with fascioliasis were significantly more likely to live with Fasciola-infected children.

INTRODUCTION

Fascioliasis is a widely distributed parasitic infection of the hepatobiliary system caused by Fasciola hepatica and Fasciola gigantica. An estimated 17 million people are infected, and 180 million people are at risk for infection globally.^1,2 Fascioliasis causes at least 35,000 disability-adjusted life years, but underestimation of the burden is possible as a result of the limited knowledge of the global prevalence.³ In the acute infection phase, juvenile parasites migrate through the liver tissue. Patients with acute infection can present with right upper quadrant pain, fever, hepatomegaly, and eosinophilia. In the chronic infection phase, adult parasites are established in the biliary tract. Patients with chronic fascioliasis can present with epigastric pain, colic, and cholangitis.⁴ However, sub-clinical infections are probably more common in the community. Weight loss and anemia are associated with subclinical infection in children and may lead to developmental delays.⁵ Fascioliasis affects livestock, causing important losses in production worldwide, which can affect food security in poor communities.⁶

Fasciola thrives in a wide range of environments and infects humans and livestock, which hinders control efforts. Control strategies are based on community prevalence.⁷ The WHO recommends treatment of cases identified in health-care settings in areas with sporadic transmission. Mass drug administration (MDA) with a single dose of triclabendazole is encouraged in areas with a high prevalence or clustering of cases.^8,9 The proposed strategies for MDA include school-based treatment and universal treatment.⁷ However, both strategies assume a homogeneous risk within the groups targeted or target very small areas, hindering implementation. They may also expose large numbers of subjects to a low triclabendazole dose that may select for resistant parasites.^10,11 Identifying control strategies that optimize resources while decreasing triclabendazole pressure on parasite populations is urgently required to stop the emergence of resistance.

Targeting subjects that share the same risk factors for fascioliasis may increase the efficiency of control measures. Risk factors for Fasciola infection include socioeconomic factors and dietary habits, such as consuming raw water vegetables and untreated water.^12–14 Age is an important risk factor, with school-age children having the greatest prevalence.¹⁵ Marcos et al.¹² suggested family clustering of Fasciola cases in a small study in the highlands of Peru. Identifying infected children may allow targeting of adults in their household as candidates for Fasciola chemotherapy. For this reason, we assessed the prevalence and factors associated with fascioliasis among adults living in the same household of children with and without Fasciola infection in the Anta Province of Peru.

METHODS

We conducted a cross-sectional study to compare the epidemiology of fascioliasis in households of children with and without the infection. Subjects were invited to participate if they were living in the same household as children enrolled in an ongoing study evaluating the impact of F. hepatica in the Anta Province of Cusco, Peru.¹⁴ Adults, 18 years or older, living in the same household for at least 2 years and with no history of fascioliasis treatment were eligible to participate. Households were enrolled consecutively if at least one member agreed to participate. Subjects were enrolled in rural communities of the districts of Anta (population 12,123), Ancahuasi (population 7,102), and Zurite (population 3,722).¹⁶ The prevalence of Fasciola infection among children in these communities was between 0% and 20%.¹⁴ Two thirds of the population in the Anta Province live in rural areas with poverty rates of up to 55%.^17,18

Demographic, epidemiological (diet, occupation, and activities in the household), and socioeconomic information was collected from subjects. The probability of living under a USD3.75 poverty line was calculated using the Simple Poverty Scorecard validated for Peru.¹⁹ Participants were asked to provide one blood sample and three stool samples on consecutive days. Stool samples were aliquoted and preserved with and without 10% formalin. Fresh samples were tested within 48 hours of collection using the Kato-Katz test. Samples preserved in formalin were tested within 1 week of collection using the Lumbreras rapid sedimentation test. All positive results were confirmed by a second observer. Positive and negative control stool specimens were included routinely to ensure quality. The blood samples were analyzed using the Fas2 ELISA (Bionoma SRL, Lima, Peru) for F. hepatica antibodies. All samples were processed and tested in the laboratory of the Universidad Peruana Cayetano Heredia and University of Texas Medical Branch Collaborative Research Center in Cusco city.

Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) v. 25.0 (SPSS IBM Corp., New York, NY). Chronic fascioliasis was defined by a positive microscopy test for F. hepatica eggs in any of the stool samples. Fasciola infection was defined as having a positive Fasciola test in blood and/or stool. The distribution of the variables was determined by calculating the frequencies, means ± SD, and medians with interquartile ranges (IQR). The χ² test was used to compare proportions between subjects with and without fascioliasis, and households with at least one infected child with households without infected children. The Student’s t-test and the Mann-Whitney U test were calculated to compare means and medians between groups, respectively. Backward logistic regression was used to model the proportion of subjects with fascioliasis in households with infected children and without the infection, adjusting for demographic and epidemiological factors. A similar model was created for the proportion of subjects with and without fascioliasis. Variables for the models were included if they were epidemiologically relevant or if P ≤ 0.1 in the univariate analysis. Statistical tests were considered significant if P < 0.05.

The study was reviewed by the Institutional Ethics Committee of Universidad Peruana Cayetano Heredia and the University of Texas Medical Branch.

RESULTS

Three hundred forty-nine adults were enrolled in the study and 23 were excluded from the analysis because of missing stool samples or information on Fasciola-infected children in their household. Three hundred twenty-six (93.4%) subjects from 213 households were included in the analysis with a mean of 1.53 (±0.76) adults included per household. Of these, 56 (26.3%) households had at least one child with fascioliasis and 157 (73.7%) households had no children with the infection. The median age was 38.6 years (IQR, 31–47.66 years) and 234 of 326 (71.8%) participants were women. The majority of the subjects (255 of 326, 78.2%) were parents of the children living in the household, and the main occupation was homemaker for 200 of 303 (66%) (Table 1). Most of the participants engaged in home (297 of 324, 91.7%) and farm activities (287 of 324, 88.6%). The Anta District (184 of 326, 56.4%) was the most common residence area. The median simple poverty score was 39 (IQR, 31–45), which was interpreted as 50% of the population having a probability of 34.4% or more of living with less than USD3.75/day.

Table 1.

Characteristics of the subjects included in the study

Characteristic	Median	IQR
Age, y	38.6	31–47.6
Crude Poverty Score Card score, pt	39	31–45

	n/N*	%
Gender
Female	234/326	71.8
Male	92/326	28.2
Relationship
Parent	255/326	78.2
Grandparent	28/326	8.6
Other	43/326	13.2
District of residence
Anta	184/326	56.4
Ancahuasi	123/326	37.7
Zurite	19/326	5.8
Occupation
Homemaker	200/303	66
Farming	68/303	22.4
Construction	10/303	3.3
Other	25/303	8.3
Lives with ≥ 1 children with Fasciola
Yes	104/326	31.9
No	222/326	68.1
Works in home activities
Yes	297/324	91.7
No	27/324	8.3
Works in farm activities
Yes	287/324	88.6
No	37/324	11.4
Water source at home
Faucet	311/322	96.6
Other	11/322	3.4

IQR = interquartile range.

^*Some denominators are less than 326 as a result of missing data.

Almost all (307 of 326, 94.2%) subjects reported eating raw vegetables, including asnapa, an herb combination used for cooking (315 of 326, 96.6%); spinach (141 of 326, 43.3%); dandelion (119 of 326, 36.5%); watercress (99 of 326, 30.4%) michi michi (Hesperoxiphiun peruvianum) (31 of 326, 9.5%); and alfalfa (Medicago sativa) (29 of 326, 8.9%). In addition, subjects reported eating raw produce that is washed with untreated water after harvest, such as carrots (175 of 326, 53.7%) and radishes (87 of 326, 26.7%). Almost all subjects (311 of 322, 96.6%) reported obtaining drinking water from a faucet outside the house piped from a municipal reservoir. More than one third (119 of 326, 36.5%) had to store water as a result of the inconsistency of the supply.

The most common protozoa detected by stool microscopy was Blastocystis hominis (91 of 321, 28.3%) followed by Giardia intestinalis (18 of 321, 5.6%). Fifty-three (16.3%) participants had at least one helminth infection detected by stool microscopy (Table 2). Chronic F. hepatica infection (24 of 326, 7.4%) was the most common helminth infection diagnosed. Twenty-four chronic Fasciola infections (7.4%) were detected by Lumbreras rapid sedimentation and 17 (5.2%) were detected using the Kato Katz test. Thirty-nine of 308 (12.7%) subjects tested positive for Fasciola antibodies by FAS2 ELISA. The total prevalence of Fasciola infection by microscopy and/or serum ELISA tests was 13.2% (43 of 326).

Table 2.

Prevalence of protozoa and helminths among study participants (N = 326)

Protozoa or helminths	N	%
Blastocystis hominis*	91	28.3
Fasciola hepatica	24	7.4
Giardia intestinalis*	18	5.6
Ascaris lumbricoides	14	4.3
Hookworm	6	1.8
Hymenolepis nana	6	1.8
Strongyloides stercoralis	5	1.5
Trichuris trichura	1	0.3

^*N = 321.

In univariate analysis, subjects with chronic fascioliasis were more likely to live in a household where there was at least one child infected with Fasciola (12 of 24 [50%] versus 92 of 302 [30.4%]; odds ratio [OR], 2.28; 95% CI, 0.98–5.27; P = 0.048), to report eating watercress (13 of 24 [54.1%] versus 86 of 300 [28.6%]; OR, 2.94; 95% CI, 1.26–6.81; P = 0.009), and to have a higher median simple poverty score (median, 43.5; IQR, 39–46.25) than subjects without fascioliasis (median simple poverty score, 38; IQR, 30.5–44; P = 0.018). Gender (P = 0.716), age (P = 0.386), and district (P = 0.346) were not associated with chronic Fasciola infection. Neither were eating other raw vegetables or being infected with other helminths or protozoa. The backward logistic regression analysis showed that living with at least one Fasciola-infected child, reporting the consumption of raw vegetables or watercress, and a lower socioeconomic level were associated independently with increased risk for having fascioliasis among adults (Table 3).

Table 3.

Backward logistic regression analysis of factors associated with chronic Fasciola infection

Factor	Adjusted odds ratio	95% CI	P value
Reports raw vegetable consumption	7.05	1.56–31.72	0.011
Lives with an infected child	4.69	1.78–12.33	0.002
Reports watercress consumption	3.09	12–8	0.019
Has a higher simple poverty score	0.93	0.88–0.98	0.009

Variables entered in the model: gender, age, living with at least one child with Fasciola, reporting raw vegetables, carrots, or watercress consumption, and simple poverty score. Hosmer and Lemeshow goodness of fit: χ², 3.7; df, 8; P = 0.87.

One third (104 of 326, 31.9%) of the participants lived in the same household with at least one child infected with F. hepatica. Subjects who lived in a household with infected children were more likely to be male, live in Zurite, have chronic Fasciola infection, and have a lower median simple poverty score. These subjects were less likely to be a homemaker and report consuming alfalfa or carrots (Table 4). No other demographic characteristics, vegetable consumption, household or farm activity, or parasite infection were associated with living in the same household with a child infected with Fasciola. In the backward logistic regression model evaluating factors associated with living with a child with fascioliasis, chronic Fasciola infection, residence in Zurite, lower poverty score, female gender, and eating alfalfa remained as independent predictors (Table 5).

Table 4.

Factors associated with living in the same household with at least one child infected with Fasciola

Factor	Household (+) N (%)	Household (–) N (%)	Odds ratio	95% CI	P value
District
Zurite	15 (14.4)	4 (1.8)	9.18	2.96–28.43	< 0.001
Other	89 (85.6)	218 (98.2)	–	–	–
Gender
Male	42 (40.4)	50 (22.5)	2.33	1.41–3.82	0.001
Female	62 (59.6)	172 (77.5)	–	–	–
Chronic Fasciola
Yes	12 (11.5)	12 (5.4)	2.28	0.99–5.27	0.048
No	92 (88.5)	210 (94.6)	–	–	–
Consumes carrots
Yes	47 (46.5)	128 (58.7)	0.61	0.38–0.98	0.042
No	54 (53.5)	90 (41.3)	–	–	–
Occupation
Homemaker	50 (52.1)	150 (72.5)	0.41	0.25–0.68	0.001
Other	46 (47.9)	57 (27.5)	–	–	–
Consumes alfalfa
Yes	2 (1.9)	27 (12.3)	0.14	0.03–0.6	0.001
No	102 (98.1)	193 (87.7)	–	–	–
Simple poverty score	35 (28–44)*	40 (32–45)*	–	–	0.03

IQR = interquartile range.

^*Median (IQR).

Table 5.

Backward logistic regression analysis of factors associated with living in the same household of a child with Fasciola hepatica infection

Factor	Adjusted odds ratio	95% CI	P value
Chronic Fasciola infection	4.22	1.6–11.16	0.004
Residence in Zurite	2.43	1.36–4.34	0.003
Lower poverty score	1.04	1.01–1.07	0.008
Female gender	0.34	0.18–0.63	0.001
Consumes alfalfa	0.16	0.03–0.78	0.023

Variables entered in the model: chronic Fasciola infection, district of residence, gender, occupation, eats alfalfa, eats carrots, poverty score. Hosmer and Lemeshow goodness of fit: χ², 5.807; df, 8; P = 0.669.

DISCUSSION

Our study found an overall prevalence of F. hepatica infection of 13% combining serological and microscopy techniques among adult household members of children who participated in an epidemiological study in the Anta Province of Cusco. The prevalence of chronic infection in adults was greater than 7%, whereas twice as many participants had positive serology. Poverty and eating raw vegetables or watercress were associated with increased risk for chronic infection. Subjects with Fasciola infection were more likely to live in the same household as an infected child. Fascioliasis is highly endemic in the highlands of Bolivia and Peru, with the greatest rate observed in children 8 to 11 years old.^15,20,21 School-based MDA has been proposed for control in these areas.^7–9 However, strategic use of triclabendazole for fascioliasis should be considered, because of decreasing drug efficacy in some regions of the world.^22,23 School screening followed by focused household treatment may reach infected people in the community more efficiently, but few studies have addressed these groups.

Twice as many subjects had positive Fas2 antibodies by ELISA compared with those passing eggs in the stool. Espinoza et al.²⁴ evaluated the Fas2 ELISA results among 634 children between 1 and 16 years old, using stool microscopy as the gold standard. They reported that Fas2 ELISA was positive for 30% to 75% more subjects than microscopy. Low-intensity infections, prior treatment, or long-term infections with less fertile parasites might decrease the sensitivity of stool microscopy. Fasciola antibody tests may become negative after successful treatment. However, the dynamics of antibody response in adults with repeated exposures has not been characterized.²⁵ The high serology prevalence in our study population might be a result of prior self-limited infections or recent exposure that did not result in established infection. A Fasciola sero-survey among nomad populations in western Iran reported a greater seroprevalence among adults 20 to 40 years old, which agrees with our findings in Cusco.²⁶ However, false-positive ELISA results are another possibility to consider. One study evaluating the Fas2 ELISA reported a positive predictive value of only 64% in a highly endemic area.²⁴ Children younger than 5 years (42%) and children older than 12 years (61%) had the lowest positive predictive values in that study.

Fascioliasis tends to occur among members of the same household in endemic areas.^12,27 We demonstrated that adults living in a household with at least one infected child were four times more likely to have fascioliasis than those living in households without an infected child. In an earlier study in the Asillo District south of the Cusco Region of Peru, 61% of children and 15% of adults from families that had at least one other member infected had chronic fascioliasis.¹² A large study in Egypt found a similar aggregation of cases in families with an increased risk for infection among children if their mothers were infected.²⁷ In contrast, Ozturhan et al.²⁸ reported no statistically significant difference between the seroprevalence found in subjects with a family history of fascioliasis (1.9%) and subjects without this history (0.5%). However, that study was performed in a low-prevalence population (0.79%) and lacked the power to demonstrate a important association among the variables. Subjects living in the same household are likely to be exposed to the same risk factors for fascioliasis because socioeconomic status and unsafe food and water are usually shared among members.

Households that had a child with fascioliasis tended to have a lower median poverty score, which suggests an association between the infection and poverty. Prior studies by our group have documented the association of fascioliasis and low socioeconomic status.^13,14 Lower socioeconomic status and lower education of the parents are associated with gastrointestinal helminth infections.^29–31 People living in poverty have limited access to safe food and water, increasing the risk for infection with food-borne pathogens, including parasites.¹⁴ Thus, poverty intertwines with parasite infections such as Fasciola to create a cycle that impacts humans from early life into adulthood.

Chronic Fasciola infection was associated with eating watercress. Watercress grows wild in Anta during the rainy season, where it is collected for personal consumption and sold in local markets. Studies in central France demonstrated colonization of wild and homegrown watercress beds with Fasciola-infected Lymnaea snails. In many instances, the colonized watercress beds were traced from human fascioliasis cases.³² In an outbreak of fascioliasis in France, subjects who consumed raw watercress or watercress soup were 86 and 22 times more likely, respectively, to be infected than control subjects.³³ In Mexico, Zumaquero-Ríos et al.³⁴ reported a strong association between reporting watercress consumption and fascioliasis among school children.

There are some limitations to this study. The parent study was a comprehensive evaluation of preschool and school-age children in the Anta Province.¹⁴ However, the number of subjects that participated in our household study was low. In addition, women were overrepresented in our sample. The study recruited subjects present in the household at the time of the visit. Men in rural communities usually leave the household early to work in farm activities and thus tend to be more difficult to include in studies. Future research efforts should include a random sample of households with or without children known to have fascioliasis to increase the representativeness of the study population.

In conclusion, in the Anta Province of the Cusco Region, the risk of fascioliasis among adults living with infected children was 4-fold greater compared with adults living with children without the infection. However, half of the adults with fascioliasis were from households that did not have infected children. Focusing on households where infected children are identified by school-based programs may help identify adults at a greater risk for Fasciola and may limit the exposure to flukicides in the population. Other strategies to identify adults with a lower risk for infection are still required. Education on dietary habits to decrease the consumption of wild watercress and increase consumption of carefully cultivated plants is needed in the Anta Province. Further research exploring factors contributing to the aggregation of cases in families, and strategies to approach difficult-to-reach household members, is warranted.