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Field evaluation of a coproantigen enzyme-linked immunosorbent assay for diagnosis of canine echinococcosis in a rural Andean village in Peru
Veterinary Parasitology 117 (2003) 37–42
Field evaluation of a coproantigen enzyme-linked immunosorbent assay for diagnosis of canine echinococcosis in a rural Andean village in Peru Luis Lopera a , Pedro L. Moro a,b,∗ , Amanda Chavez c , Glicerio Montes d , Armando Gonzales c , Robert H. Gilman a,b a Asociacion Benefica PRISMA, Lima, Peru Department of International Health, Johns Hopkins University, Baltimore, MD, USA School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru d Veterinary Clinic, SAIS Tupac Amaru, Junin, Peru b
c
Received 3 February 2003; received in revised form 2 July 2003; accepted 19 July 2003
Abstract One hundred and six dogs (61 males and 45 females) were examined for Echinococcus granulosus infection in a farming cooperative in the central highlands of Peru during November 1998. Canine echinococcosis was diagnosed using direct microscopic examinations of purged feces following arecoline purging and a coproantigen-detection enzyme-linked immunosorbent assay (ELISA) for E. granulosus. Mean age was 2 years with a range of 3 months to 9 years. The overall prevalence of canine echinococcosis using the ELISA test was 79% (84/106). Seventy-four dogs were successfully purged with arecoline. The frequency of canine echinococcosis was 82 (61/74) and 34% (25/74) by the coproantigen ELISA test and arecoline purging, respectively. The sensitivity and specificity of the coproantigen ELISA test was 88 and 95%, respectively. We found this assay to be especially advantageous in remote geographical areas. In future control programs against echinococcosis in Peru and other areas where E. granulosus is endemic the coproantigen ELISA should be used for the surveillance of the dog population. © 2003 Elsevier B.V. All rights reserved. Keywords: Echinococcus granulosus; Dog; Coproantigen ELISA; Diagnosis; Peru
∗ Corresponding author. Present address: Department of International Health, The Johns Hopkins School of Hygiene and Public Health, 615 N. Wolfe St. W3501, Baltimore, MD 21205, USA. Tel.: +1-410-614-3959; fax: +1-410-614-6060. E-mail address: [email protected] (P.L. Moro).
0304-4017/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2003.07.019
38
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
1. Introduction Echinococcus granulosus infection is an important zoonotic infection in sheep raising regions of Peru. Recent epidemiological studies have demonstrated echinococcal prevalences of 9, 32 and 98% in humans, dogs and sheep, respectively (Moro et al., 1997). The development of sensitive and specific diagnostic techniques for the detection of echinococcosis in dogs is important for the study and control of echinococcosis. Ante-mortem diagnosis of canine echinococcosis has traditionally been performed by using arecoline salts for purgation followed by microscopic examination of the purged feces for the adult tapeworm (WHO, 1981). Although the specificity of this method is 100%, it is biohazardous, time-consuming, requires trained personnel and has variable sensitivity (WHO, 1981). An important advance has been the development of a coproantigen enzyme-linked immunosorbent assay (ELISA) for diagnosis of canine echinococcosis (Allan et al., 1992). A preliminary survey in an endemic village in Peru was used to demonstrate if optimal results would result in verification of a coproantigen ELISA used for diagnosis of canine echinococcosis (Moro et al., 1999). Use of the coproantigen ELISA assay would be of great value in communities planning to initiate echinococcosis control programs. One such community in Peru is the farming cooperative of Tupac Amaru where a pilot control program against echinococcosis was conducted during the 1970s (Diaz et al., 1984). During January–March 1998 local authorities in this community undertook a campaign to diagnose canine echinococcosis using an arecoline survey of echinococcosis. The purpose of the present study was to assess the ability of this newly developed coproantigen ELISA to diagnose canine echinococcosis in this community and to compare it with fecal examination following arecoline purging. 2. Material and methods 2.1. Study sites Tupac Amaru is a farming cooperative in the central Peruvian Andes at altitudes ranging from 3600 to 4300 m above sea level. The village has several smaller farms some of which are quite distant from major roads. Villagers use dogs routinely to care for their sheep. Fecal samples from parasite free dogs to be used as negative controls were collected at the San Marcos School of Veterinary Medicine Clinic in Lima city, an area known to be free of E. granulosus infection. 2.2. Coproantigen ELISA Fecal samples were collected from the rectum of dogs, prior to arecoline purging. Samples were placed in 5% phosphate-buffered saline formalin solution and kept at +4 ◦ C until tested. The coproantigen ELISA was performed as described by Allan et al. (1992), with the following modification: for each plate 100 ul of substrate solution containing sodium citrate (0.1 M), 4.1 ml of citric acid (0.1 M), and 10 ul of 30% hydrogen peroxide was added to each well. The reaction was allowed to proceed for 15 min at room temperature and was
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
39
stopped with 25 ul of 4 M sulfuric acid. Plates were read at 490 nm with a Kinetic Microplate reader. The same positive and negative controls were used on every plate. To correct for interplate variations, a correction factor was used as previously described (Verastegui et al., 1992). 2.3. Arecoline purging of dogs Dogs were given an oral dose of arecoline hydrobromide (Sigma), 4 mg/kg, as previously described (WHO, 1981). Fecal samples were collected from dogs that purged successfully and examined according to WHO guidelines (WHO, 1981). 3. Results One hundred and sixteen dogs were brought by their owners for examination. Fecal samples were obtained from 106 dogs. Ten dogs were excluded due to difficulty in sample collection. Mean age was 2 years with a range of 3 months to 9 years. Sixty-one male (58%) and 45 (42%) female dogs were sampled. The overall prevalence of canine echinococcosis using the ELISA test was 79% (84/106). There was no significant difference in prevalence between male and female dogs (50/61 (82%) and 34/45 (76%), respectively; P = 0.42 by the χ2 -test). Seventy-four (70%) of these dogs were successfully purged and the purged fecal specimens were examined for E. granulosus tapeworms (Table 1). Microscope examination of purged samples revealed that 34% (25/74) were infected with E. granulosus tapeworms. By contrast the prevalence of echinococcosis in this subsample of dogs as measured by the coproantigen ELISA was 82% (61/74). The mean intensity was 95 (range 1–572) for 22 ELISA-positive dogs and 4 (range 1–8) for 3 ELISA-negative dogs. The sensitivity of the coproantigen ELISA was 88% (22/25), based on our gold standard of an arecoline purge. The specificity of the ELISA determined in dogs from Lima city was 95% (18/19) (Table 2). Table 1 Comparison of coproantigen ELISA with arecoline purge positivity in 106 dogs Test
Purge +
Purge −
Did not purge
Coproantigen + Coproantigen −
22 3
39 10
23 9
84 22
Total
25
49
32
106a
a
Total
Ten dogs, not included here, were not examined due to difficulty in sample collection.
Table 2 Sensitivity and specificity of the ELISA for detecting E. granulosus coproantigens in fecal samples of dogs Dog population
Coproantigen-positive/ total number of dogs
Sensitivity (%)
Specificity (%)
Sheepdogs from Tupac Amaru, Peru Dogs from Lima city, Peru
22/25 1/19
88 –
– 95
40
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
No significant differences in prevalences using the ELISA or microscopic fecal examination were noted when dog age was considered. The agreement between both tests was poor (k = 0.06). 4. Discussion We demonstrated that in remote areas where echinococcosis is endemic the coproantigen ELISA might be conveniently and effectively used for the study of canine echinococcosis. The high prevalence of canine echinococcosis (82%) among sheepdogs suggests that these animals are heavily infected with E. granulosus in the Peruvian highlands. This high prevalence is not surprising given their easy access to hydatid infected offal, either given to the dogs by their owners and/or from scavenging livestock that die in the field (Moro et al., 1997). This is supported by the higher intensity noted among positive dogs. In a previous study we found a lower overall prevalence of canine echinococcosis in another endemic community in Peru using the same coproantigen ELISA test (Moro et al., 1999). The prevalence of echinococcosis among shepherd dogs in that community was found to be as high (88%), as the rate found in this study. In the present study the sensitivity of the coproantigen ELISA was 88% in comparison with the results of arecoline purgation. Arecoline diagnosis has in its own inherent limitations and thus our sensitivity estimates are based on dogs that successfully purged and were E. granulosus positive. Nevertheless, the sensitivity reported here is similar to that reported in dogs with high worm counts in Jordan where the coproantigen ELISA was compared to necropsy (El-Shehabi et al., 2000). Ideally sensitivity and specificity should be assessed in dogs examined at necropsy rather than in dogs purged with arecoline (El-Shehabi et al., 2000). However, this option was not acceptable to the community. We used dogs from middle-class owners from Lima city as negative controls as these had received anti-parasitic treatment and lived in areas where E. granulosus is virtually non-existent. The specificity was found to be as high as previously reported (Allan et al., 1992; Craig et al., 1995; El-Shehabi et al., 2000). It is important to point out that the prevalence figures reported here are representative of local sheepdogs as virtually all dogs sampled were used for the care of sheep raised in the field. The overall prevalence of the entire dog population in the community would likely be lower if all dogs had been included. We observed a number of advantages with the coproantigen ELISA that make it suitable for surveillance of large dog populations. Sample collection for the coproantigen ELISA test was easier, faster to perform and required less personnel than the cumbersome, laborious and risky task of collecting fecal samples following arecoline purgation. The lower prevalence of E. granulosus infection following purgation when compared to the prevalence using the ELISA test is likely due to the inherent limitations of arecoline, specially when used in field studies. Unlike arecoline purgation, which requires taking dogs to purge sites and concentration of dogs in specific places, fecal samples for coproantigen testing were collected in the field for some of the dogs surveyed without need to transport them to a specific location. Although most dogs were taken to specific locations, a significant number of dogs were sampled in the field because these dogs could not be purged due to lack of secure facilities for purgation, pregnant female dogs or lack of owner’s consent.
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
41
Additional advantages of the ELISA test have been reported in Australia where experimental infection of dogs with E. granulosus showed that coproantigen may be detectable early in the course of infection (Jenkins et al., 2000). These findings, if confirmed in naturally infected canids, may be of importance for hydatid control programs because the detection of prepatent infections of E. granulosus in dogs will identify infected dogs for treatment before the tapeworms have reached patency and eggs are released into the environment. In addition, the Australian study suggests that coproantigens in the environment may remain stable even after exposure to harsh climatic conditions, such as those experienced in the Peruvian highlands. If so, the ELISA test could potentially be used to assess the degree of environmental contamination in potentially endemic communities where direct study of dog populations may not be feasible. A major limitation with the coproantigen ELISA test, at least on the short term is the substantial cost of acquiring reagents and an ELISA reader. Another important limitation could be its application in areas of low endemicity where the predictive value positive would be expected to be low and where potential cross-reactions with other Taenia sp. may be expected as has been described in Cyprus (Christophi et al., 2002). We believe that the coproantigen ELISA is a promising test and should be used for diagnosis of echinococcosis in dogs and as part of control programs. The test would be especially helpful in remote geographical areas. In future control programs against echinococcosis in Peru and other areas where E. granulosus is endemic the coproantigen ELISA should be used for the surveillance of the dog population.
Acknowledgements This study was funded by Consejo Nacional de Ciencia y Tecnolog´ıa (CONCYTEC). We wish to thank Dr. Peter Schantz for manuscript review and the people and authorities of the farming cooperative of Tupac Amaru in Junin, Peru. References Allan, J.C., Craig, P.S., Garcia Noval, J., Mencos, F., Liu, D., Wang, Y., Wen, Y., Zhou, P., Stringer, R., Rogan, M., Zeyhle, E., 1992. Coproantigen detection for immunodiagnosis of echinococcosis and taeniasis in dogs and humans. Parasitology 104, 347–355. Christophi, G., Deplazes, P., Christophi, N., Tanner, I., Economides, P., Eckert, J., 2002. Screening of dogs for Echinococcus granulosus coproantigen in a low endemic situation in Cyprus. Vet. Parasitol. 104, 299–306. Craig, P.S., Gasser, R.B., Parada, L., Cabrera, P., Parietti, S., Borgues, C., Acuttis, A., Agulla, J., Snowden, K., Paolillo, E., 1995. Diagnosis of canine echinococcosis: comparison of coproantigen and serum antibody tests with arecoline purgation in Uruguay. Vet. Parasitol. 56, 293–301. Diaz, V.M., Naquira, F., Coltorti, E.A., Ocharan, A.M., Bullon, F., Elliot, A., Contreras, O., Tantalean, M., Huiza, A., Naquira, C., 1984. La hidatidosis en el Peru: importancia del inmunodiagnostico y de los estudios seroepidemiologicos. Acta Med. Per. 11, 21–28. El-Shehabi, F.S., Kamhawi, S.A., Schantz, P.M., Craig, P.S., Abdel-Hafez, S.K., 2000. Diagnosis of canine echinococcosis: comparison of coproantigen detection with necropsy in stray dogs and red foxes from northern Jordan. Parasite 7, 83–90. Jenkins, D.J., Fraser, A., Bradshaw, H., Craig, P.S., 2000. Detection of Echinococcus granulosus coproantigens in Australian canids with natural or experimental infection. J. Parasitol. 86, 140–145.
42
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
Moro, P.L., McDonald, J., Gilman, R.H., Silva, B., Verastegui, M., Malqui, V., Lescano, G., Falcon, N., Montes, G., Bazalar, H., 1997. Epidemiology of Echinococcus granulosus infection in the Central Andes of Peru. Bull. World Health Organ. 75, 553–561. Moro, P.L., Bonifacio, N., Gilman, R.H., Lopera, L., Silva, B., Takumoto, R., Verastegui, M., Cabrera, L., 1999. Field diagnosis of Echinococcus granulosus infection among intermediate and definitive hosts in an endemic focus of human cystic echinococcosis. Trans. R. Soc. Trop. Med. Hyg. 93, 611–615. Verastegui, M., Moro, P., Guevara, A., Rodriguez, T., Miranda, E., Gilman, R.H., 1992. Enzyme-linked immunoelectrotransfer blot test for the diagnosis of human hydatid disease. J. Clin. Microbiol. 30, 1557–1561. WHO (World Health Organization), 1981. In: J. Eckert, M.A. Gemmell, E.J.L. Soulsby (Eds.), Guidelines for Surveillance, Prevention and Control of Echinococcosis/Hydatidosis. FAO/UNEP/WHO. WHO, Geneva, Switzerland, 265 pp.
Field evaluation of a coproantigen enzyme-linked immunosorbent assay for diagnosis of canine echinococcosis in a rural Andean village in Peru Luis Lopera a , Pedro L. Moro a,b,∗ , Amanda Chavez c , Glicerio Montes d , Armando Gonzales c , Robert H. Gilman a,b a Asociacion Benefica PRISMA, Lima, Peru Department of International Health, Johns Hopkins University, Baltimore, MD, USA School of Veterinary Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru d Veterinary Clinic, SAIS Tupac Amaru, Junin, Peru b
c
Received 3 February 2003; received in revised form 2 July 2003; accepted 19 July 2003
Abstract One hundred and six dogs (61 males and 45 females) were examined for Echinococcus granulosus infection in a farming cooperative in the central highlands of Peru during November 1998. Canine echinococcosis was diagnosed using direct microscopic examinations of purged feces following arecoline purging and a coproantigen-detection enzyme-linked immunosorbent assay (ELISA) for E. granulosus. Mean age was 2 years with a range of 3 months to 9 years. The overall prevalence of canine echinococcosis using the ELISA test was 79% (84/106). Seventy-four dogs were successfully purged with arecoline. The frequency of canine echinococcosis was 82 (61/74) and 34% (25/74) by the coproantigen ELISA test and arecoline purging, respectively. The sensitivity and specificity of the coproantigen ELISA test was 88 and 95%, respectively. We found this assay to be especially advantageous in remote geographical areas. In future control programs against echinococcosis in Peru and other areas where E. granulosus is endemic the coproantigen ELISA should be used for the surveillance of the dog population. © 2003 Elsevier B.V. All rights reserved. Keywords: Echinococcus granulosus; Dog; Coproantigen ELISA; Diagnosis; Peru
∗ Corresponding author. Present address: Department of International Health, The Johns Hopkins School of Hygiene and Public Health, 615 N. Wolfe St. W3501, Baltimore, MD 21205, USA. Tel.: +1-410-614-3959; fax: +1-410-614-6060. E-mail address: [email protected] (P.L. Moro).
0304-4017/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2003.07.019
38
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
1. Introduction Echinococcus granulosus infection is an important zoonotic infection in sheep raising regions of Peru. Recent epidemiological studies have demonstrated echinococcal prevalences of 9, 32 and 98% in humans, dogs and sheep, respectively (Moro et al., 1997). The development of sensitive and specific diagnostic techniques for the detection of echinococcosis in dogs is important for the study and control of echinococcosis. Ante-mortem diagnosis of canine echinococcosis has traditionally been performed by using arecoline salts for purgation followed by microscopic examination of the purged feces for the adult tapeworm (WHO, 1981). Although the specificity of this method is 100%, it is biohazardous, time-consuming, requires trained personnel and has variable sensitivity (WHO, 1981). An important advance has been the development of a coproantigen enzyme-linked immunosorbent assay (ELISA) for diagnosis of canine echinococcosis (Allan et al., 1992). A preliminary survey in an endemic village in Peru was used to demonstrate if optimal results would result in verification of a coproantigen ELISA used for diagnosis of canine echinococcosis (Moro et al., 1999). Use of the coproantigen ELISA assay would be of great value in communities planning to initiate echinococcosis control programs. One such community in Peru is the farming cooperative of Tupac Amaru where a pilot control program against echinococcosis was conducted during the 1970s (Diaz et al., 1984). During January–March 1998 local authorities in this community undertook a campaign to diagnose canine echinococcosis using an arecoline survey of echinococcosis. The purpose of the present study was to assess the ability of this newly developed coproantigen ELISA to diagnose canine echinococcosis in this community and to compare it with fecal examination following arecoline purging. 2. Material and methods 2.1. Study sites Tupac Amaru is a farming cooperative in the central Peruvian Andes at altitudes ranging from 3600 to 4300 m above sea level. The village has several smaller farms some of which are quite distant from major roads. Villagers use dogs routinely to care for their sheep. Fecal samples from parasite free dogs to be used as negative controls were collected at the San Marcos School of Veterinary Medicine Clinic in Lima city, an area known to be free of E. granulosus infection. 2.2. Coproantigen ELISA Fecal samples were collected from the rectum of dogs, prior to arecoline purging. Samples were placed in 5% phosphate-buffered saline formalin solution and kept at +4 ◦ C until tested. The coproantigen ELISA was performed as described by Allan et al. (1992), with the following modification: for each plate 100 ul of substrate solution containing sodium citrate (0.1 M), 4.1 ml of citric acid (0.1 M), and 10 ul of 30% hydrogen peroxide was added to each well. The reaction was allowed to proceed for 15 min at room temperature and was
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
39
stopped with 25 ul of 4 M sulfuric acid. Plates were read at 490 nm with a Kinetic Microplate reader. The same positive and negative controls were used on every plate. To correct for interplate variations, a correction factor was used as previously described (Verastegui et al., 1992). 2.3. Arecoline purging of dogs Dogs were given an oral dose of arecoline hydrobromide (Sigma), 4 mg/kg, as previously described (WHO, 1981). Fecal samples were collected from dogs that purged successfully and examined according to WHO guidelines (WHO, 1981). 3. Results One hundred and sixteen dogs were brought by their owners for examination. Fecal samples were obtained from 106 dogs. Ten dogs were excluded due to difficulty in sample collection. Mean age was 2 years with a range of 3 months to 9 years. Sixty-one male (58%) and 45 (42%) female dogs were sampled. The overall prevalence of canine echinococcosis using the ELISA test was 79% (84/106). There was no significant difference in prevalence between male and female dogs (50/61 (82%) and 34/45 (76%), respectively; P = 0.42 by the χ2 -test). Seventy-four (70%) of these dogs were successfully purged and the purged fecal specimens were examined for E. granulosus tapeworms (Table 1). Microscope examination of purged samples revealed that 34% (25/74) were infected with E. granulosus tapeworms. By contrast the prevalence of echinococcosis in this subsample of dogs as measured by the coproantigen ELISA was 82% (61/74). The mean intensity was 95 (range 1–572) for 22 ELISA-positive dogs and 4 (range 1–8) for 3 ELISA-negative dogs. The sensitivity of the coproantigen ELISA was 88% (22/25), based on our gold standard of an arecoline purge. The specificity of the ELISA determined in dogs from Lima city was 95% (18/19) (Table 2). Table 1 Comparison of coproantigen ELISA with arecoline purge positivity in 106 dogs Test
Purge +
Purge −
Did not purge
Coproantigen + Coproantigen −
22 3
39 10
23 9
84 22
Total
25
49
32
106a
a
Total
Ten dogs, not included here, were not examined due to difficulty in sample collection.
Table 2 Sensitivity and specificity of the ELISA for detecting E. granulosus coproantigens in fecal samples of dogs Dog population
Coproantigen-positive/ total number of dogs
Sensitivity (%)
Specificity (%)
Sheepdogs from Tupac Amaru, Peru Dogs from Lima city, Peru
22/25 1/19
88 –
– 95
40
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
No significant differences in prevalences using the ELISA or microscopic fecal examination were noted when dog age was considered. The agreement between both tests was poor (k = 0.06). 4. Discussion We demonstrated that in remote areas where echinococcosis is endemic the coproantigen ELISA might be conveniently and effectively used for the study of canine echinococcosis. The high prevalence of canine echinococcosis (82%) among sheepdogs suggests that these animals are heavily infected with E. granulosus in the Peruvian highlands. This high prevalence is not surprising given their easy access to hydatid infected offal, either given to the dogs by their owners and/or from scavenging livestock that die in the field (Moro et al., 1997). This is supported by the higher intensity noted among positive dogs. In a previous study we found a lower overall prevalence of canine echinococcosis in another endemic community in Peru using the same coproantigen ELISA test (Moro et al., 1999). The prevalence of echinococcosis among shepherd dogs in that community was found to be as high (88%), as the rate found in this study. In the present study the sensitivity of the coproantigen ELISA was 88% in comparison with the results of arecoline purgation. Arecoline diagnosis has in its own inherent limitations and thus our sensitivity estimates are based on dogs that successfully purged and were E. granulosus positive. Nevertheless, the sensitivity reported here is similar to that reported in dogs with high worm counts in Jordan where the coproantigen ELISA was compared to necropsy (El-Shehabi et al., 2000). Ideally sensitivity and specificity should be assessed in dogs examined at necropsy rather than in dogs purged with arecoline (El-Shehabi et al., 2000). However, this option was not acceptable to the community. We used dogs from middle-class owners from Lima city as negative controls as these had received anti-parasitic treatment and lived in areas where E. granulosus is virtually non-existent. The specificity was found to be as high as previously reported (Allan et al., 1992; Craig et al., 1995; El-Shehabi et al., 2000). It is important to point out that the prevalence figures reported here are representative of local sheepdogs as virtually all dogs sampled were used for the care of sheep raised in the field. The overall prevalence of the entire dog population in the community would likely be lower if all dogs had been included. We observed a number of advantages with the coproantigen ELISA that make it suitable for surveillance of large dog populations. Sample collection for the coproantigen ELISA test was easier, faster to perform and required less personnel than the cumbersome, laborious and risky task of collecting fecal samples following arecoline purgation. The lower prevalence of E. granulosus infection following purgation when compared to the prevalence using the ELISA test is likely due to the inherent limitations of arecoline, specially when used in field studies. Unlike arecoline purgation, which requires taking dogs to purge sites and concentration of dogs in specific places, fecal samples for coproantigen testing were collected in the field for some of the dogs surveyed without need to transport them to a specific location. Although most dogs were taken to specific locations, a significant number of dogs were sampled in the field because these dogs could not be purged due to lack of secure facilities for purgation, pregnant female dogs or lack of owner’s consent.
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
41
Additional advantages of the ELISA test have been reported in Australia where experimental infection of dogs with E. granulosus showed that coproantigen may be detectable early in the course of infection (Jenkins et al., 2000). These findings, if confirmed in naturally infected canids, may be of importance for hydatid control programs because the detection of prepatent infections of E. granulosus in dogs will identify infected dogs for treatment before the tapeworms have reached patency and eggs are released into the environment. In addition, the Australian study suggests that coproantigens in the environment may remain stable even after exposure to harsh climatic conditions, such as those experienced in the Peruvian highlands. If so, the ELISA test could potentially be used to assess the degree of environmental contamination in potentially endemic communities where direct study of dog populations may not be feasible. A major limitation with the coproantigen ELISA test, at least on the short term is the substantial cost of acquiring reagents and an ELISA reader. Another important limitation could be its application in areas of low endemicity where the predictive value positive would be expected to be low and where potential cross-reactions with other Taenia sp. may be expected as has been described in Cyprus (Christophi et al., 2002). We believe that the coproantigen ELISA is a promising test and should be used for diagnosis of echinococcosis in dogs and as part of control programs. The test would be especially helpful in remote geographical areas. In future control programs against echinococcosis in Peru and other areas where E. granulosus is endemic the coproantigen ELISA should be used for the surveillance of the dog population.
Acknowledgements This study was funded by Consejo Nacional de Ciencia y Tecnolog´ıa (CONCYTEC). We wish to thank Dr. Peter Schantz for manuscript review and the people and authorities of the farming cooperative of Tupac Amaru in Junin, Peru. References Allan, J.C., Craig, P.S., Garcia Noval, J., Mencos, F., Liu, D., Wang, Y., Wen, Y., Zhou, P., Stringer, R., Rogan, M., Zeyhle, E., 1992. Coproantigen detection for immunodiagnosis of echinococcosis and taeniasis in dogs and humans. Parasitology 104, 347–355. Christophi, G., Deplazes, P., Christophi, N., Tanner, I., Economides, P., Eckert, J., 2002. Screening of dogs for Echinococcus granulosus coproantigen in a low endemic situation in Cyprus. Vet. Parasitol. 104, 299–306. Craig, P.S., Gasser, R.B., Parada, L., Cabrera, P., Parietti, S., Borgues, C., Acuttis, A., Agulla, J., Snowden, K., Paolillo, E., 1995. Diagnosis of canine echinococcosis: comparison of coproantigen and serum antibody tests with arecoline purgation in Uruguay. Vet. Parasitol. 56, 293–301. Diaz, V.M., Naquira, F., Coltorti, E.A., Ocharan, A.M., Bullon, F., Elliot, A., Contreras, O., Tantalean, M., Huiza, A., Naquira, C., 1984. La hidatidosis en el Peru: importancia del inmunodiagnostico y de los estudios seroepidemiologicos. Acta Med. Per. 11, 21–28. El-Shehabi, F.S., Kamhawi, S.A., Schantz, P.M., Craig, P.S., Abdel-Hafez, S.K., 2000. Diagnosis of canine echinococcosis: comparison of coproantigen detection with necropsy in stray dogs and red foxes from northern Jordan. Parasite 7, 83–90. Jenkins, D.J., Fraser, A., Bradshaw, H., Craig, P.S., 2000. Detection of Echinococcus granulosus coproantigens in Australian canids with natural or experimental infection. J. Parasitol. 86, 140–145.
42
L. Lopera et al. / Veterinary Parasitology 117 (2003) 37–42
Moro, P.L., McDonald, J., Gilman, R.H., Silva, B., Verastegui, M., Malqui, V., Lescano, G., Falcon, N., Montes, G., Bazalar, H., 1997. Epidemiology of Echinococcus granulosus infection in the Central Andes of Peru. Bull. World Health Organ. 75, 553–561. Moro, P.L., Bonifacio, N., Gilman, R.H., Lopera, L., Silva, B., Takumoto, R., Verastegui, M., Cabrera, L., 1999. Field diagnosis of Echinococcus granulosus infection among intermediate and definitive hosts in an endemic focus of human cystic echinococcosis. Trans. R. Soc. Trop. Med. Hyg. 93, 611–615. Verastegui, M., Moro, P., Guevara, A., Rodriguez, T., Miranda, E., Gilman, R.H., 1992. Enzyme-linked immunoelectrotransfer blot test for the diagnosis of human hydatid disease. J. Clin. Microbiol. 30, 1557–1561. WHO (World Health Organization), 1981. In: J. Eckert, M.A. Gemmell, E.J.L. Soulsby (Eds.), Guidelines for Surveillance, Prevention and Control of Echinococcosis/Hydatidosis. FAO/UNEP/WHO. WHO, Geneva, Switzerland, 265 pp.