Camargo et al. Parasites & Vectors 2010, 3:11 http://www.parasitesandvectors.com/content/3/1/11 RESEARCH Open Access Capillariaisis (Trichurida, Trichinellidae, Capillaria hepatica) in the Brazilian Amazon: low pathogenicity, low infectivity and a novel mode of transmission Luis Marcelo Aranha Camargo1,2*, Juliana de Souza Almeida Aranha Camargo2, Luana Janaina de Souza Vera2, Pedro di Tarique Crispim Barreto3, Eudes Kang Tourinho4, Marcia Maria de Souza5 Abstract Background: Human capillariasis caused by Capillaria hepatica (syn. Calodium hepaticum) is a rare disease with no more than 40 cases registered around the world. Classically, the disease has severe symptoms that mimic acute hepatitis. Natural reservoirs of C. hepatica are urban rodents (Mus musculus and Rattus novergicus) that harbor their eggs in the liver. After examining the feces of 6 riverine inhabitants (Rio Preto area, 8° 03’S and 62° 53’ Wto8°14’S and 62° 52’W) of the State of Rondonia, Brazil, and identifying C. hepatica eggs in their feces, the authors decided to investigate the real dimension of these findings by looking for two positive signals. Methods: Between June 1st and 15th, 2008, 246 out of 304 individuals were clinically examined. Blood samples were collected, kept under -20°C, and test by the indirect immunofluorescence technique. Results: The first positive signal was the presence of specific antibodies at 1:150 dilution, which indicates that the person is likely to have been exposed to eggs, most likely non-infective eggs, passing through the food chain or via contaminated food (total prevalence of 34.1%). A second more specific signal was the presence of antibodies at higher titers, thus indicating true infection. Conclusions: The authors concluded that only two subjects were really infected (prevalence of 0.81%); the rest was false-positives that were sensitized after consuming non-embryonated eggs. The present study is the first one carried out in a native Amazonian population and indicates the presence of antibodies against C. hepatica in this population. The results further suggest that the transmission of the parasite occurs by the ingestion of embryonated eggs from human feces and/or carcasses of wild animals. The authors propose a novel mode of transmission, describing the disease as a low pathogenic one, and showing low infectivity. Background which infect the bowels, the lower breathing airways Capillariasis is a cosmopolitan helminthiasis with zoono- and the liver, respectively [11]. tic characteristics. Its etiological agent infects many spe- Traditionally, most authors consider liver capillariasis cies of mammals, birds, fish and invertebrate animals a rare disease. Among at least 40 cases of parasitism [1-10]. The etiological agents belong to the phylum caused by C. hepatica that have been registered in the Nematoda, order Trichurida, family Trichinellidae and literature, five occurred in Brazil [12,13]. Moreover, eggs genus Capillaria. This genus contains 300 species of of C. hepatica have been identified in the feces of indivi- which three are well known human parasites, namely: duals of Brazilian indigenous populations [14,15]. Capillaria philippinensis, C. aerophila and C. hepatica, Eggs can be ingested from the soil or from carcasses of dead animals. Animal models have shown that the larvae of C. hepatica hatch at the level of the cecum, * Correspondence: [email protected] penetrate the mucous membrane and reach the porta 1Department of Parasitology, University of Sao Paulo, Sao Paulo, Brazil © 2010 Camargo et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Camargo et al. Parasites & Vectors 2010, 3:11 Page 2 of 6 http://www.parasitesandvectors.com/content/3/1/11 system until they lodge in the hepatic parenchyma. signal was the presence of antibodies at higher titers, Finally, after 1 month, they become adult worms. Ferti- thus indicating true infection. lized eggs spread in groups around the females, which die within thirty days. The eggs remain viable and Methods immature for approximately 120 days. In order for Study Area embryogenesis to occur, the eggs must reach the envir- This work was performed in the locality of the Preto onment, which in this case is possible only after the River, at the intersection of Machado River with death of the infected host and disintegration of its car- Madeira River, Rondonia State, western Brazilian cass. Alternatively, ingestion of organs (eg., liver) con- Amazon. taining non-embryonated eggs and their further The study area (8° 03’Sand62°53’ Wto8°14’Sand elimination through the feces, will also induce embryo- 62° 52’W) is inhabited by 304 individuals. These people genesis, thus resulting in infective eggs in the soil are descendants of the “rubber soldiers” of the XIX and [16,17]. XX centuries, of native populations, and from immi- Clinical manifestations are related to the inflammatory grants from the south and southwestern regions of the reaction it causes in the adjacent tissues. Because they country. This area lacks electricity and medical care. affect the hepatic tissue, clinical forms similar to those Houses are made of wood with thatched or asbestos of acute viral hepatitis and the classical triad (fever, roofs (Fig. 1). There are no toilets and excrements are hepatomegaly and eosinophilia) may be present [18]. thrown around the houses or dumped in cesspits After diagnosing 6 riverine inhabitants of the State of located 10 to 20 meters from the houses. Water is taken Rondonia, Brazil, eliminating eggs of C. hepatica in their from the river or from small wells known as “cacimbas” feces, the authors decided to investigate the real dimen- anditisconsumedunfilteredandwithoutanytreat- sion of these findings by looking for positive signals at ment. People earn their living working the land for their two levels. The first positive signal was the presence of subsistence, selling the excess product to bargaining specific antibodies at the 1/150 dilution, which indicates small merchants. Some people sell the pulp of native that the person is likely to have been exposed to eggs, fruits (cacao, cupuassu, etc.) in Porto Velho, located most likely non-infective eggs, passing through the food more than 250 km away. The basic diet is fish, manioc chain or via contaminated food. A second more specific flour, seasonal fruits and wild animals, such as monkeys, Figure 1 Typical house and riverine inhabitants along the Rio Preto river, Rondonia, Amazon region, Brazil. Camargo et al. Parasites & Vectors 2010, 3:11 Page 3 of 6 http://www.parasitesandvectors.com/content/3/1/11 peccaries (Tayassu spp.), paca (Agouti paca), cotia for all the serological positive patients at the same time (Dasyprocta aguti), deer, alligators, birds, etc. and using the same biological samples. Population Data Collection Statistical Analyses In the past 6 years, researchers from the University of Information was stored in an Excell® data file and ana- São Paulo have been studying the Preto River area, lyzed by Epi Info 6.2. Qualitative variables (sex, age registering its population. During this period the groups, positive/negative test and place of origin) were researchers diagnosed 6 inhabitants who presented analyzed using the chi-square test and multivariate C. hepatica eggs in their feces. Because the community logistic regression. Quantitative variables (time living in is very small, all individuals were examined by the medi- the Amazon and in the study area, family income and cal staff, except those who were not present in the com- age) were analyzed through the nonparametric Mann- munity between June 1st and 15th, 2008. From the 304 Whitney U test, since these variables showed a non-nor- permanent inhabitants, 246 were present at the time of mal distribution for the Shapiro-Wilk test. The signifi- the study and all were examined. cance level was set at 0.05. Collection and processing of biological samples Subjects read and signed a term of consent prior to the Ethical approval collection of samples. A volume of 10 mL of blood was This study was submitted to the Ethics Committee of collected from each subject in dry tubes by venous the São Lucas School, registered under number PT/ puncture, after the due asepsis of the forearm. Blood CEP/10/08. samples were kept at room temperature for 3 to 4 hours and then centrifuged at 3,000 rpm for 10 minutes. Each Results serum sample was kept at -20°C, until the serological A total of 246 subjects (81%) out of the 304 permanent exam was carried out. inhabitants of the community had their serum samples Serum samples were diluted in saline buffered solution examined. The population was basically composed by (PBS) at 50% to 1/150 and tested against paraffin cuts 194 native individuals (79%) and 52 (21%) people cur- containing mice livers with C. hepatica eggs and worms, rently living in the area but original from outside the according to the technique proposed previously [19]. The Amazon (immigrants). 41% reported to earn their living same author suggests a cut-off of 1/400 to diagnose false from agriculture and fishing, 28% performed activities from- true-positive cases. False-positive cases occur after related to home care and 28% were students. The rest the ingestion and immunological sensibilization by non- of the population was composed of civil servants and embryonated eggs. On the other hand, true-positive cases small dealers. When examined, 10 individuals (4%) pre- are the ones that ingested embryonated eggs and harbor sented positive haemoscopy for malaria (Plasmodium the worms in the liver tissue. Results proved to be posi- vivax and P. falciparum). tive (>1/150) were scored as weak (PI), median (PII) and Over ninety percent (91.7%) of the people interviewed strong (PIII), based on fluorescence intensity, according informed they had eaten paca and/or agouti, and/or to personal criteria of two different examiners.