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Observations on helminth infections of free-living and captive rheas (Rhea americana) in Brazil
Veterinary Parasitology 129 (2005) 169–172 www.elsevier.com/locate/vetpar
Short communication
Observations on helminth infections of free-living and captive rheas (Rhea americana) in Brazil C.D. Zettermann a,*, A.A. Nascimento a, J.A. Tebaldi a, M.J.P. Szabo´ b a
Department of Preventive Veterinary and Animal Reproduction of FCAV-UNESP, BR, Rodovia Acesso Prof. Paulo Donato Castellane, s/no., Jaboticabal, SP, Brazil b Franca University, UNIFRAN, BR, Volunteer Researcher at the Department of Veterinary Pathology of FCAV-UNESP, Brazil Accepted 4 December 2004
Abstract The present work describes helminth infection of eight free-living and 12 captive rheas (Rhea americana) from, respectively, Pantanal of Mato Grosso do Sul State, and Jaboticabal, Sa˜o Paulo State, Brazil. Captive birds were young and had a high mortality rate, while free-living birds were adult and apparently healthy. Infections were evaluated by post-mortem examination of internal organs and recovery of helminths using standard parasitological procedures. Seven species of nematodes (Sicarius uncinipenis, Torquatoides crotophaga, Deletrocephalus dimidiatus, D. cesarpintoi, Paradeletrocephalus minor, Capillaria venteli and Dicheilonema rheae) and two species of cestodes (Houttuynia struthionis and Chapmania tauricolis) were identified. P. minor, which inhabits the large intestine, was the most common helminth in free-living birds (63.9%). In captive rheas, a mean parasitic load of 173 helminths per host was found. The gizzard of these birds was the most parasitized organ and S. uncinipenis was most common (92.5%). Parasitism of free-living and captive birds and associated pathology are discussed. # 2005 Published by Elsevier B.V. Keywords: Rhea americana; Epidemiology; Helminths; Prevalence; Brazil
1. Introduction Wildlife preservation is under pressure worldwide, but, at the same time, some wild animals can be viewed as a source of animal protein. Knowledge about parasitism in these animals is desirable when managed under natural conditions and also for production in * Corresponding author. E-mail addresses: [email protected], [email protected] (C.D. Zettermann). 0304-4017/$ – see front matter # 2005 Published by Elsevier B.V. doi:10.1016/j.vetpar.2004.12.015
captive conditions. Additionally, description of parasites and parasitic diseases in free-living and captive animals may help to evaluate importance of host– parasite relationships in each environment. Rheas (Rhea americana) belong to the ratite group, a group of flightless birds. This bird species is nowadays commercially farmed in Brazil (AGCE, 2000). Unfortunately, data on helminth parasites of rheas is scarce. For this reason, the purpose of this study was to investigate helminth parasites species in captive and wildlife birds.
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C.D. Zettermann et al. / Veterinary Parasitology 129 (2005) 169–172
The results may help for proper management of captive rheas and hence improve commercial farming and allow an evaluation of sanitary conditions of freeliving birds in endangered areas.
2. Material and methods
2.3. Histopathology Due to high infestation loads and severe disease, gizzard samples of captive birds highly infested with Sicarius uncinipenis were fixed in buffered formalin, pH 7.0, and processed for microscopic evaluation according to routine histological procedures.
2.1. Animals 3. Results and discussion Eight adult wild and 12 young captive rheas were examined. Wild rheas were hunted1 during winter of 1990 and 1991, in Coxin and Pedro Gomes counties, Pantanal of Mato Grosso do Sul (sub-region of Paiagua´ s), Brazil. These animals were apparently healthy. Young captive rheas were from the Wild Animal Sector of the Agrarian and Veterinary Science Faculty from Sa˜ o Paulo State University, Jaboticabal, Brazil (FCAV-UNESP). These animals died in summer of 1997/1998 and showed anorexia and emaciation before death. 2.2. Helminth recovery All birds were necropsied. The gastrointestinal tract was divided according to anatomical segments, opened and washed. Contents were fixed in Railliet & Henry solution. All helminths were identified and counted. Helminths in the gastric mucosae, oral and nasal cavity, eyes, oviduct, wombs, kidneys, trachea, lungs, liver and air sacs were also identified and counted. For identification, nematodes were diafanized in 80% acetic acid solution and Faya creosote and clarified as described by Freitas and Lent (1947a,b); Schmidt (1970); Freitas and Almeida (1935); Chabaud (1975–1976); Pence and Casto (1976) and Rodrigueˆ s and Rodrigueˆ s (1981). Infection indicators were calculated according to Margolis et al. (1982). Cestodes were processed for identification as described by Travassos (1950). Briefly, scolices of cestodes were flattened between two slides and kept in Railliet and Henry solution. Later, scolices were stained in acetic-carmin solution and washed in 70% alcohol. Identification was as described by Schmidt (1970). 1 Brazilian National Environment Institute (IBAMA) authorised hunt (license no. 089/90-DEVIS-IBAMA).
Results are summarised in Table 1. All examined birds were positive. Nine species of helminths were identified from captive and free-living birds: seven species of nematodes (S. uncinipenis, Torquatoides crotophaga, Deletrocephalus dimidiatus, D. cesarpintoi, Paradeletrocephalus minor, Capillaria venteli and Dicheilonema rheae) and two species of cestodes (Houttuynia struthionis and Chapmania tauricolis). The most prevalent helminth in captive birds was S. uncinipenis, in the gizzard. Infection is believed to originate from the introduction of naturally infected animals. High density of animals and age of birds (young) in captivity might have favoured this parasite. It can also be supposed that the high intensity of infection of the captive birds might have been related to the presence of an intermediate host, probably an arthropod (Schimidt and Roberts, 1977). The high prevalence and high average intensity of infection of the birds with S. uncinipenis may have caused the high mortality in the captive birds. Treatment of birds with anti-helmintics decreased mortality rate. S. uncinipenis was observed as a reddish worm inserted between the koilin layer and the mucosa of the gizzard of birds. The mucosa of the gizzard was thickened, congested and displayed a few petechiae close to the parasite. Path-like depressions could be observed in the mucosa and which were attributed to the movement of the parasite. In the most infested animals the koilin layer could be easily removed and was, in a few cases, destroyed. Microscopic examination revealed only a slight inflammatory infiltrate composed of a few mononuclear cells and eosinophils or heterophils close to parasites and oedema of the mucosa. No erythrocytes or iron could be detected inside the worms indicating lack of blood feeding. Pathogenicity of S. uncinipenis is thus believed to be
C.D. Zettermann et al. / Veterinary Parasitology 129 (2005) 169–172
171
Table 1 Helminth species in the gastrointestinal segments and air sacs from eight free-living adult rheas (A) from Coxim and Pedro Gomes counties, Pantanal of Mato Grosso of Sul, Brazil, and 12 young rheas and (B) maintained in captive in the facilities of the wild animal sector of FCAVUNESP, Jaboticabal, SP, Brazil Helminth species
Habitat
Infection indexes Intensity
Average intensity
Abundance
Prevalence (%)
Total
A
A
B
A
B
A
0.4 –
160.1 3.0
25.0 –
91.6 41.6
A
B
Gizzard
1–2 –
15–536 1–25
1.5 (2) –
Oesophagus
1–17
–
9.0 (2)
–
2.2
–
25.0
Small intestine
1–50
–
24.5 (4)
–
12.2
–
H. struthionis Deletrocephalidae D. dimidiatus Large intestine D. cesarpintoi P. minor Filariidae D. rheae Air sacs
7–20
–
13.5 (2)
–
3.4
3–507
4–41
120.6 (6)
4–60 1–43
– –
36.0 (2) 364.0 (5)
– –
1–14
–
5.5 (6)
–
Habronematidae S. uncinipenis T. crotophaga Trichuridae C. venteli Davaineidae C. tauricolis
B 174.7 (11) 7.3 (11)
11.9 (10)
(%)a B
A
B
3 0
1922 36
0.5 –
92.5 1.8
–
18
0
1.0
–
50.5
–
98
0
3.5
–
–
25.0
–
27
0
1.0
–
9.9
75.0
83.3
724
119
25.5
5.7
9.0 227.5
– –
25.0 62.5
– –
72 1820
0 0
3.0 64.0
– –
4.1
–
75.0
–
33
0
1.5
–
2848
2077
90.5
Total Number of infected animals is presented between brackets. a Percentage in relation to the total number of helminths recovered from either free-living or captive birds.
associated with ingesta spoliation and interference with the gizzards function. Eight species of helminths were recovered from the free-living rheas. The high numbers found in these birds were probably associated with the exposure to a more varied parasitic fauna in wildlife. At the same time, free-living rheas were apparently healthy as shown by their good physical condition, the vigorous attempts to escape from hunt and lack of meaningful lesions at necropsy. Some observations on the parasitic species found in free-living birds are, however, interesting. S. uncinipenis was less common. The most common species were the large intestine Deletrocephalidae nematodes P. minor and D. dimidiatus. The average intensity for P. minor and D. dimidiatus was, respectively, of 364 and 121. Specimens were found in, respectively, 5 and 6 out of the 8 birds examined. These species are considered of relevance due to their blood-feeding habits which, according to Craig and Diamond (1996) could be responsible, in high infections, to the onset of an anaemia syndrome in rheas. However, no anaemia was
observed. C. venteli and T. crotophaga were found, respectively, in the oesophagus and gizzard of freeliving rheas. These species are known to parasitise, respectively, the roseate spoonbill (Ajaia ajaja) (Pence and Casto, 1976) and the guira cuckoo (Guira guira) (Rodrigueˆ s and Rodrigueˆ s, 1981) and, to best of our knowledge, have never been described from rheas before. Their presence can be attributed to crossinfections among different birds living in the same environment. Straightforward comparison of observations is not possible due to many differences between the helminth infection of free-living and captive rheas (age of birds, time and location of death and breeding environment). However, results of this study show that young rheas in captivity must undergo a strict parasitary control. It is desirable to have treatment followed by a quarantine period when new birds are introduced to a commercial rhea farms. On the other hand, free-living rheas may have a rich helminthic fauna which is not necessarily associated to disease.
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C.D. Zettermann et al. / Veterinary Parasitology 129 (2005) 169–172
References AGCE, 2000. Associac¸a˜ o Gau´ cha dos Criadores de Emas. http:// www.zooway.com.br, August 2000. Chabaud, A.G., 1975-6. n.3 Keys to genera of the order Spirurida. Part 2. Spiruroidea, Habronematoidea and Acuarioidea. In: Anderson, R.G., Chabaud, A.G., Willmott, S. (Eds.), Cih Keys of the Nematode Parasites of Vertebrates. CAB International, Wallingford. Craig, T.M., Diamond, P.L., 1996. Parasites of ratites. In: Tully, Jr., T.N., Shane, S.M., Ratite, (Eds.), Management Medicine and Surgery. 1st ed. Krieger Publishing Company, Malabar, FL, pp. 115–126. Freitas, J.F.T., Almeida, J.L., 1935. Sobre os nematoda capillariinae parasitas de esoˆ fago e papo de aves. Mem. Inst. Oswaldo Cruz. 30 (2), 123–167. Freitas, J.F.T., Lent, H., 1947a. ‘Spiruroidea’ parasitos de ‘Rheiformes’ (Nematoda). Mem. Inst. Oswaldo Cruz. 45 (4), 743– 760.
Freitas, J.F.T., Lent, H., 1947b. Revisa˜ o da subfamı´lia ‘Deletrocephalinae’ Railliet & Henry 1916 (Nematoda: Strongyloidea). Rev. Bras. Biol. 7 (1), 73–100. Margolis, L., Esch, G., Holmes, J.C., Ruris, A.M., Schad, G.A., 1982. The use of ecological terms in parasitology (report of an Hoc Committee of the American Society of Parasitologists). J. Parasitol. 68 (1), 131–133. Pence, D.B., Casto, S., 1976. Torquatoides crotophaga Williams (Nematoda: Spiruridae: Habronematinae) from cuculiform birds in Texas. Proceed. Helmintol. Soc. (Washington) 43 (1), 24–28. Rodrigueˆ s, S.S., Rodrigueˆ s, H.O., 1981. Contribuic¸a˜ o ao conhecimento da fauna helmintolo´ gica do anu branco (Guira guira G. M.). At. Soc. Biol. (Rio de Janeiro) 22, 39–56. Schmidt, G.D., 1970. The Tapeworms. Brown Company Publishers, Duduque, IA, pp. 266. Schimidt, G.D., Roberts, L.S., 1977. Foundation of Parasitology. C.V. Mosby Company, St. Louis, Missouri, p. 604. Travassos, L., 1950. Introduc¸a˜ o ao Estudo da Helmintologia. Rev. Bras. Biol. 169.
Short communication
Observations on helminth infections of free-living and captive rheas (Rhea americana) in Brazil C.D. Zettermann a,*, A.A. Nascimento a, J.A. Tebaldi a, M.J.P. Szabo´ b a
Department of Preventive Veterinary and Animal Reproduction of FCAV-UNESP, BR, Rodovia Acesso Prof. Paulo Donato Castellane, s/no., Jaboticabal, SP, Brazil b Franca University, UNIFRAN, BR, Volunteer Researcher at the Department of Veterinary Pathology of FCAV-UNESP, Brazil Accepted 4 December 2004
Abstract The present work describes helminth infection of eight free-living and 12 captive rheas (Rhea americana) from, respectively, Pantanal of Mato Grosso do Sul State, and Jaboticabal, Sa˜o Paulo State, Brazil. Captive birds were young and had a high mortality rate, while free-living birds were adult and apparently healthy. Infections were evaluated by post-mortem examination of internal organs and recovery of helminths using standard parasitological procedures. Seven species of nematodes (Sicarius uncinipenis, Torquatoides crotophaga, Deletrocephalus dimidiatus, D. cesarpintoi, Paradeletrocephalus minor, Capillaria venteli and Dicheilonema rheae) and two species of cestodes (Houttuynia struthionis and Chapmania tauricolis) were identified. P. minor, which inhabits the large intestine, was the most common helminth in free-living birds (63.9%). In captive rheas, a mean parasitic load of 173 helminths per host was found. The gizzard of these birds was the most parasitized organ and S. uncinipenis was most common (92.5%). Parasitism of free-living and captive birds and associated pathology are discussed. # 2005 Published by Elsevier B.V. Keywords: Rhea americana; Epidemiology; Helminths; Prevalence; Brazil
1. Introduction Wildlife preservation is under pressure worldwide, but, at the same time, some wild animals can be viewed as a source of animal protein. Knowledge about parasitism in these animals is desirable when managed under natural conditions and also for production in * Corresponding author. E-mail addresses: [email protected], [email protected] (C.D. Zettermann). 0304-4017/$ – see front matter # 2005 Published by Elsevier B.V. doi:10.1016/j.vetpar.2004.12.015
captive conditions. Additionally, description of parasites and parasitic diseases in free-living and captive animals may help to evaluate importance of host– parasite relationships in each environment. Rheas (Rhea americana) belong to the ratite group, a group of flightless birds. This bird species is nowadays commercially farmed in Brazil (AGCE, 2000). Unfortunately, data on helminth parasites of rheas is scarce. For this reason, the purpose of this study was to investigate helminth parasites species in captive and wildlife birds.
170
C.D. Zettermann et al. / Veterinary Parasitology 129 (2005) 169–172
The results may help for proper management of captive rheas and hence improve commercial farming and allow an evaluation of sanitary conditions of freeliving birds in endangered areas.
2. Material and methods
2.3. Histopathology Due to high infestation loads and severe disease, gizzard samples of captive birds highly infested with Sicarius uncinipenis were fixed in buffered formalin, pH 7.0, and processed for microscopic evaluation according to routine histological procedures.
2.1. Animals 3. Results and discussion Eight adult wild and 12 young captive rheas were examined. Wild rheas were hunted1 during winter of 1990 and 1991, in Coxin and Pedro Gomes counties, Pantanal of Mato Grosso do Sul (sub-region of Paiagua´ s), Brazil. These animals were apparently healthy. Young captive rheas were from the Wild Animal Sector of the Agrarian and Veterinary Science Faculty from Sa˜ o Paulo State University, Jaboticabal, Brazil (FCAV-UNESP). These animals died in summer of 1997/1998 and showed anorexia and emaciation before death. 2.2. Helminth recovery All birds were necropsied. The gastrointestinal tract was divided according to anatomical segments, opened and washed. Contents were fixed in Railliet & Henry solution. All helminths were identified and counted. Helminths in the gastric mucosae, oral and nasal cavity, eyes, oviduct, wombs, kidneys, trachea, lungs, liver and air sacs were also identified and counted. For identification, nematodes were diafanized in 80% acetic acid solution and Faya creosote and clarified as described by Freitas and Lent (1947a,b); Schmidt (1970); Freitas and Almeida (1935); Chabaud (1975–1976); Pence and Casto (1976) and Rodrigueˆ s and Rodrigueˆ s (1981). Infection indicators were calculated according to Margolis et al. (1982). Cestodes were processed for identification as described by Travassos (1950). Briefly, scolices of cestodes were flattened between two slides and kept in Railliet and Henry solution. Later, scolices were stained in acetic-carmin solution and washed in 70% alcohol. Identification was as described by Schmidt (1970). 1 Brazilian National Environment Institute (IBAMA) authorised hunt (license no. 089/90-DEVIS-IBAMA).
Results are summarised in Table 1. All examined birds were positive. Nine species of helminths were identified from captive and free-living birds: seven species of nematodes (S. uncinipenis, Torquatoides crotophaga, Deletrocephalus dimidiatus, D. cesarpintoi, Paradeletrocephalus minor, Capillaria venteli and Dicheilonema rheae) and two species of cestodes (Houttuynia struthionis and Chapmania tauricolis). The most prevalent helminth in captive birds was S. uncinipenis, in the gizzard. Infection is believed to originate from the introduction of naturally infected animals. High density of animals and age of birds (young) in captivity might have favoured this parasite. It can also be supposed that the high intensity of infection of the captive birds might have been related to the presence of an intermediate host, probably an arthropod (Schimidt and Roberts, 1977). The high prevalence and high average intensity of infection of the birds with S. uncinipenis may have caused the high mortality in the captive birds. Treatment of birds with anti-helmintics decreased mortality rate. S. uncinipenis was observed as a reddish worm inserted between the koilin layer and the mucosa of the gizzard of birds. The mucosa of the gizzard was thickened, congested and displayed a few petechiae close to the parasite. Path-like depressions could be observed in the mucosa and which were attributed to the movement of the parasite. In the most infested animals the koilin layer could be easily removed and was, in a few cases, destroyed. Microscopic examination revealed only a slight inflammatory infiltrate composed of a few mononuclear cells and eosinophils or heterophils close to parasites and oedema of the mucosa. No erythrocytes or iron could be detected inside the worms indicating lack of blood feeding. Pathogenicity of S. uncinipenis is thus believed to be
C.D. Zettermann et al. / Veterinary Parasitology 129 (2005) 169–172
171
Table 1 Helminth species in the gastrointestinal segments and air sacs from eight free-living adult rheas (A) from Coxim and Pedro Gomes counties, Pantanal of Mato Grosso of Sul, Brazil, and 12 young rheas and (B) maintained in captive in the facilities of the wild animal sector of FCAVUNESP, Jaboticabal, SP, Brazil Helminth species
Habitat
Infection indexes Intensity
Average intensity
Abundance
Prevalence (%)
Total
A
A
B
A
B
A
0.4 –
160.1 3.0
25.0 –
91.6 41.6
A
B
Gizzard
1–2 –
15–536 1–25
1.5 (2) –
Oesophagus
1–17
–
9.0 (2)
–
2.2
–
25.0
Small intestine
1–50
–
24.5 (4)
–
12.2
–
H. struthionis Deletrocephalidae D. dimidiatus Large intestine D. cesarpintoi P. minor Filariidae D. rheae Air sacs
7–20
–
13.5 (2)
–
3.4
3–507
4–41
120.6 (6)
4–60 1–43
– –
36.0 (2) 364.0 (5)
– –
1–14
–
5.5 (6)
–
Habronematidae S. uncinipenis T. crotophaga Trichuridae C. venteli Davaineidae C. tauricolis
B 174.7 (11) 7.3 (11)
11.9 (10)
(%)a B
A
B
3 0
1922 36
0.5 –
92.5 1.8
–
18
0
1.0
–
50.5
–
98
0
3.5
–
–
25.0
–
27
0
1.0
–
9.9
75.0
83.3
724
119
25.5
5.7
9.0 227.5
– –
25.0 62.5
– –
72 1820
0 0
3.0 64.0
– –
4.1
–
75.0
–
33
0
1.5
–
2848
2077
90.5
Total Number of infected animals is presented between brackets. a Percentage in relation to the total number of helminths recovered from either free-living or captive birds.
associated with ingesta spoliation and interference with the gizzards function. Eight species of helminths were recovered from the free-living rheas. The high numbers found in these birds were probably associated with the exposure to a more varied parasitic fauna in wildlife. At the same time, free-living rheas were apparently healthy as shown by their good physical condition, the vigorous attempts to escape from hunt and lack of meaningful lesions at necropsy. Some observations on the parasitic species found in free-living birds are, however, interesting. S. uncinipenis was less common. The most common species were the large intestine Deletrocephalidae nematodes P. minor and D. dimidiatus. The average intensity for P. minor and D. dimidiatus was, respectively, of 364 and 121. Specimens were found in, respectively, 5 and 6 out of the 8 birds examined. These species are considered of relevance due to their blood-feeding habits which, according to Craig and Diamond (1996) could be responsible, in high infections, to the onset of an anaemia syndrome in rheas. However, no anaemia was
observed. C. venteli and T. crotophaga were found, respectively, in the oesophagus and gizzard of freeliving rheas. These species are known to parasitise, respectively, the roseate spoonbill (Ajaia ajaja) (Pence and Casto, 1976) and the guira cuckoo (Guira guira) (Rodrigueˆ s and Rodrigueˆ s, 1981) and, to best of our knowledge, have never been described from rheas before. Their presence can be attributed to crossinfections among different birds living in the same environment. Straightforward comparison of observations is not possible due to many differences between the helminth infection of free-living and captive rheas (age of birds, time and location of death and breeding environment). However, results of this study show that young rheas in captivity must undergo a strict parasitary control. It is desirable to have treatment followed by a quarantine period when new birds are introduced to a commercial rhea farms. On the other hand, free-living rheas may have a rich helminthic fauna which is not necessarily associated to disease.
172
C.D. Zettermann et al. / Veterinary Parasitology 129 (2005) 169–172
References AGCE, 2000. Associac¸a˜ o Gau´ cha dos Criadores de Emas. http:// www.zooway.com.br, August 2000. Chabaud, A.G., 1975-6. n.3 Keys to genera of the order Spirurida. Part 2. Spiruroidea, Habronematoidea and Acuarioidea. In: Anderson, R.G., Chabaud, A.G., Willmott, S. (Eds.), Cih Keys of the Nematode Parasites of Vertebrates. CAB International, Wallingford. Craig, T.M., Diamond, P.L., 1996. Parasites of ratites. In: Tully, Jr., T.N., Shane, S.M., Ratite, (Eds.), Management Medicine and Surgery. 1st ed. Krieger Publishing Company, Malabar, FL, pp. 115–126. Freitas, J.F.T., Almeida, J.L., 1935. Sobre os nematoda capillariinae parasitas de esoˆ fago e papo de aves. Mem. Inst. Oswaldo Cruz. 30 (2), 123–167. Freitas, J.F.T., Lent, H., 1947a. ‘Spiruroidea’ parasitos de ‘Rheiformes’ (Nematoda). Mem. Inst. Oswaldo Cruz. 45 (4), 743– 760.
Freitas, J.F.T., Lent, H., 1947b. Revisa˜ o da subfamı´lia ‘Deletrocephalinae’ Railliet & Henry 1916 (Nematoda: Strongyloidea). Rev. Bras. Biol. 7 (1), 73–100. Margolis, L., Esch, G., Holmes, J.C., Ruris, A.M., Schad, G.A., 1982. The use of ecological terms in parasitology (report of an Hoc Committee of the American Society of Parasitologists). J. Parasitol. 68 (1), 131–133. Pence, D.B., Casto, S., 1976. Torquatoides crotophaga Williams (Nematoda: Spiruridae: Habronematinae) from cuculiform birds in Texas. Proceed. Helmintol. Soc. (Washington) 43 (1), 24–28. Rodrigueˆ s, S.S., Rodrigueˆ s, H.O., 1981. Contribuic¸a˜ o ao conhecimento da fauna helmintolo´ gica do anu branco (Guira guira G. M.). At. Soc. Biol. (Rio de Janeiro) 22, 39–56. Schmidt, G.D., 1970. The Tapeworms. Brown Company Publishers, Duduque, IA, pp. 266. Schimidt, G.D., Roberts, L.S., 1977. Foundation of Parasitology. C.V. Mosby Company, St. Louis, Missouri, p. 604. Travassos, L., 1950. Introduc¸a˜ o ao Estudo da Helmintologia. Rev. Bras. Biol. 169.