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Sarcocystis sp. in guanaco (Lama guanicoe) and effect of temperature on its viability
Veterinary Parasitology, 15 (1984) 95--101 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
95
SARCOCYSTIS SP. IN GUANACO (LAMA GUANICOE) AND EFFECT OF TEMPERATURE ON ITS VIABILITY
T.R. G O R M A N ,
H.A. A L C A i N O
and H. M U i ~ O Z
University o f Chile, School o f Veterinary Medicine, Casilla 49 Correo 15, La Granja, Santiago (Chile) C. CUNAZZA
Ministry o f Agriculture, C.O.N.A.F., Casilla 1237, Punta Arenas (Chile) (Accepted for publication 19 October 1983)
ABSTRACT Gorman, T.R., Alcaino, H.A., Mufioz, H. and Cunazza, C., 1984. Sarcocystis sp. in guanaco (Lama guanicoe) and effect of temperature on its viability. Vet. Parasitol., 15: 95--101. The biology of the Sarcocystis sp. that infect guanacoes was studied by feeding the infected meat to dogs, cats, rats and mice. Tissues from guanaco, heavily infected with macrocysts, were fed to these animals and their faeces collected daily and examined for the presence or absence of sporocysts. It was shown that only dogs were suitable definitive hosts. The effect of cooking and freezing on the viability of this protozoan organism was also investigated. Freezing to -18°C and -24°C and cooking were effective for inactivating Sarcocystis in guanaco meat. These methods could therefore be used instead of condemning guanaco carcasses infected with Sarcocystis.
INTRODUCTION
The study of the genus Sarcocystis has been stimulated by the discovery of its coccidian nature and its heterogeneous cycle involving carnivores as definitive hosts and herbivores as intermediate hosts (Fayer, 1972; Heydorn and Rommel, 1972; R o m m e l et al., 1972). There is now much information about the identificationof new hosts and species,characteristics of their life-cycle,importance of acute infections, and also economical impact of naturally- and experimentally-infectedanimals (Markus et al., 1974; Dubey, 1976; Melhorn et al., 1978; R o m m e l et al.,1979; Stalheim et al.,1980; Boch et al.,1980; Erber and Burgkart, 1981). The parasite has been identified in the muscles of wild herbivores, as well as in domestic-animal species, and the life~ycle has been investigated through experimental inoculation of possible definitive hosts (Emnett and Hugghins, 1979; Tongson and Pablo~ 1979; Dubey, 1980a, b; Collins, 1981; Kuraev, 1981). 0304-4017/84/$03.00
© 1984 Elsevier Science Publishers B.V.
96 Sarcosporidiosis in Chile is prevalent in domestic-animal species (Gorman et al., 1981), and is usually present as microscopic cysts which are n o t detected by routine inspection at abattoirs. The infection has also been reported frequently in alpaca (Lama pacos), guanaco (Lama guanicoe) (Cunazza, 1980), and p u d u (Pudu pudu) (Rioseco et al., 1976), b u t in these species it is generally present as macroscopic cysts, easily seen by the naked eye. Information obtained by officers of the Corporaci6n Nacional Forestal (CONAF), Ministry o f Agriculture, has led to the recognition of the infection as a problem in guanacoes, of the austral region of Chile. Serious efforts to encourage the breeding of this autochthonous species of mammal are being carried o u t in that region, since sheep farming has c o m p e t e d with and displaced guanaco from many areas of its natural environment. Sarcosporidiosis presents an economic problem, since its macroscopic appearance leads to rejection of some tissues and in severe cases to rejection of the whole carcass. It is n o t known whether Sarcocystis of guanaco can produce h u m a n infection. This study was undertaken to investigate some biological aspects and possible definitive hosts of the Sarcocystis of guanaco, as well as the effect of freezing and cooking on the viability of this protozoan. Heat treatment o f infected meat could prevent its rejection and thus encourage the breeding and commercial management o f the guanaco. MATERIALS AND METHODS In a preliminary study it was determined that dogs excreted sporocysts after ingesting guanaco meat infected with sarcocysts. In this study, dogs, cats, rats and mice were investigated as hosts through feeding experiments with meat infected with abundant visible cysts of Sarcocystis. Apart from the dogs, all the animals were raised in a laboratory and had n o t ingested meat before. Dogs were obtained through private dealers and they were kept in quarantine for 4 months before the experiments were started. During this period the dogs were treated with anthelmintics and an antiprotozoan p r o d u c t (Tinidazol 50 mg kg -1, twice a day for 7 days) to remove residual infections. Dogs and cats were housed in individual cages, and coprological examinations were performed dally on each of them for a period of 2 months before ingestion of the infected meat. A flotation technique with zinc sulphate solution was used. Eight rats and 8 mice were each infected with 3 macroscopic cysts of Sarcocystis from infected guanaco meat. F o u r dogs and 4 cats were fed daily 250 g and 50 g, respectively, of the infected meat for 5 days. Another cat and dog received dally 4 dissected macroscopic cysts each, for 4 days. The second experiment was c o n d u c t e d to determine whether Sarcocystis remained infectious after cooking or freezing.
97
In this study 13 dogs were used as follows: Group 1, uninfected controls -- 2 dogs that were fed only commercial food; Group 2, infected controls -- 5 dogs that were fed daily on 250 g of guanaco meat infected with Sarcocystis for 5 days; Groups 3, 4, 5, each group contained 2 dogs, each dog was fed daily on 250 g of infected guanaco meat for 5 days. The meat had been kept for 5 days at - 1 8 ° C or - 2 4 ° C , or had been c o o k e d above 60°C. In both experiments dogs' and cats' faeces were individually examined every day for 30 days, beginning on the day of the first feeding. When sporocysts were present, the period was extended for 90 days. Rats and mice were evaluated through daffy examination of pooled samples. The number of sporocysts was recorded and their average size was determined through 50 measurements in each infected animal. The prolonged effect of refrigeration was also studied b y feeding infected meat, refrigerated for 30 days, to a dog. RESULTS
Cats, rats and mice remained negative to the presence of sporocysts for as long as 30 days after the ingestion of Sarcocystis-infected guanaco meat. The 4 dogs that had ingested the infected meat, excreted sporocysts after a pre-patency of 9--16 days (:~ = 12; S.D. = 2.5) (Table I). The dog which was fed the macrocysts also became infected. The patent period varied between 19 and 61 days with an average of 45.6 days (S.D. = 16.7) (Table I).
TABLE I Pre-patent and patent period of Sarcocystis sp. from guanaco in experimentally-infected
dogs No. o f days Pre-patent
Patent
Dog No. 1 2 3 4 5a
9 12 12 11 16
61 58 42 48 19
S.D.
12.0 2.5
45.6 16.7
aInfeeted with dissected macroscopic cysts.
98
The number of sporocysts excreted varied throughout the elimination phase. The shedding~urve of sporocysts from 4 dogs is shown in Fig. 1. Average size of sporocysts were 14.6/~ long X 10.6/~ wide (S.D. = 0.41 and 0.58, respectively).
3r
--
Dog 1
--- Dog 2
2 ~
rl
; IV
~l
eo
,;
0 L 0
~
\./
!i
A
'\,
v
'/
AL~,1~. ' ',
•
',
V
L
A
'"
a
:
",_l__J." --
Dog 3
---
Dog 4
;. i
20
,,t
;\
'
10
,~
v\x.\ A
"i
al
z
,
30
40
Days
after
50
t
60
feeding
Fig. 1. Excretion of sporocysts by 4 dogs fed guanaco meat infected with Sarcocystis. No. o f sporocysts/g of faeces expressed as Log + 1.
The second experiment demonstrated that dogs fed either cooked or frozen meat infected with Sarcocystis, did not excrete sporocysts for the 30-day observation period. However, control dogs that had ingested refrigerated meat, became infected with the parasite since they shed sporocysts. The dog fed the meat that had been refrigerated for 30 days also excreted sporocysts. It was found that dogs receiving only commercially prepared pelleted food, did not excrete sporocysts during the 30-day observation period (uninfected controls). DISCUSSION
Of the species studied, only dogs proved to be suitable definitive hosts for the 8arcocystis species that infect guanacoes. The choice of species screened as possible definitive hosts was based on the existence of similar
99
and related species in the guanaco environment, in the austral region of Chile. Foxes and wild dogs are abundant in this region. F r o m our results it is natural to presume that under natural conditions of the guanaco habitat, these species of carnivores m a y play an important role in the lifecycle o f Sarcocystis. It would be interesting to study the relationship of other wild carnivores such as prey- or carrion~ating birds (condors) that may act as predators on guanacoes. On the other hand, since cats did n o t become infected it is possible that wild felids such as the p u m a are n o t suitable hosts for this Sarcocystis sp. It is therefore recommended that further studies involving these species should be carried out. As the protozoan organisms were present as macroscopic and microscopic cysts, it was assumed that there could exist a difference o f infectivity among the 2 forms. However, by feeding dissected macroscopic cysts to 1 dog (No. 5) and 1 cat, it was observed that both forms were infective to dogs, b u t n o t to cats. The amount o f sporocysts excreted by the infected dogs was variable although a peak was observed around the 18th and 31st day post-infection. After 36 days their number started to decline and no special pattern of variation was observed as reported previously (Fig. 1) (Fayer, 1977; E m n e t t and Hugghins, 1982). Freezing and cooking seem to be suitable methods for destroying the protozoan organisms in the meat. However, refrigeration temperatures of 5°C, did n o t affect their viability. In addition, it was observed that prolonged refrigeration, for 30 days, was quite ineffective in destroying the organisms since a dog fed with such treated meat excreted sporocysts. Extraneous and accidental infections with organisms during the experiment were ruled out, since the dogs fed only pelleted food did n o t have any sporocysts u p o n coprological examinations throughout the experiment. These findings are in agreement with those reported by Gestrich and H e y d o r n (1974), Fayer (1975), and Leek and Fayer (1978), in that cooking and freezing are effective methods for inactivating this protozoa. It is n o t known yet whether Sarcocystis-infected guanaco meat might induce human infections. These treatments of the meat present a means for salvaging guanaco meat which would otherwise be destroyed due to sarcosporidiosis, and hence a motivation to breed guanaco as a productive species. With regard to the name of this Sarcocystis species, Quiroga et al. proposed in 1969 the name S. tilopodi for the p r o t o z o a in guanacoes. Although no studies have been done on infection of guanacoes with sporocysts excreted by dogs, the new trends in nomenclature would indicate that a suitable name would be S. guanicoe-canis in order to distinguish it from S. lama-canis in animals o f the Lama genus.
100 ACKNOWLEDGEMENTS
Financial support was provided by Corporacidn Nacional Forestal (CONAF), Ministerio de Agricultura. REFERENCES Boch, J., Hennings, R. and Erber, M., 1980. The economic importance of sarcosporidiosis (Sarcocystis suicanis) in pigs under fattening conditions. Analysis of fields trials. Berl. Muench. Tieraerztl. Wochenschr., 93: 420---423. Collins, G.H., 1981. Studies on Sarcocystis species. VIII: Sarcocystis and Toxoplasma in red deer (Cervus elaphus). N.Z. Vet. J., 29: 126--127. Cunazza, C., 1980. El guanaco, importante recurso natural renovable de Magallanes, 2a edn. Corporaci6n Nacional Forestal, Ministerio de Agricultura, Chile, Publ. No. 17, pp. 1--17. Dubey, J.P., 1976. A review of Sarcocystis of domestic animals and other coccidia of cats and dogs. J. Am. Vet. Med. Assoc., 169: 1061--1078. Dubey, J.P., 1980a- Coyote as a final host for Sarcocystis species of goats, sheep, cattle, elk, bison, and moose in Montana. Am. J. Vet. Res., 41: 1227--1229. Dubey, J.P., 1980b. Sarcocystis species in moose (Alces alces), bison (Bison bison), and pronghorn (Antilocapra americana) in Montana. Am. J. Vet. Res., 41: 2063-2065. Emnett, Ch.W. and Hugghins, E.J., 1979. Sarcocystis of deer in South Dakota. Proc. S.D. Acad. Sci., 58: 168. Emnett, Ch.W. and Hugghins, E.J., 1982. Sarcocystis of deer in South Dakota. J. Wildl. Dis., 18: 187--193. Erber, M. and Burgkart, M., 1981. Economic losses due to sarcosporidiosis (Sarcocystis sp.) in fattening lambs. Prakt. Tierarzt, 62: 422--424. Fayer, R., 1972. Gametogony of Sarcocystis sp. in cell culture. Science, 175: 65--67. Fayer, R., 1975. Effects of refrigeration, cooking, and freezing on Sarcocystis in beef from retail food stores. Proc. Helminthol. Soc. Wash., 42: 138--140. Fayer, R., 1977. Production of Sarcocystis cruzi sporocysts by dogs fed experimentallyinfected and naturally-infected beef. J. Parasitol., 63: 1935--1937. Gestrich, R. and Heydorn, A.O., 1974. Survival time of Sarcocystis cyst in the meat of slaughter animals. Berl. Muench. Tieraerztl. Wochenschr., 87: 475--476. Gorman, T., Alcafno, H. and Robles, M., 1981. Sarcosporidiosis en las especies de abasto beneficiadas en la Regidn Metropolitana de Chile. Arch. Med. Vet., 13: 39--49. Heydorn, A.O. and Rommel, M., 1972. The life cycle of Sarcosporidea. II. Dogs and cats as transmitters of bovine Sarcosporidea. Berl. Muench. Tieraerztl. Wochensehr., 85: 121--123. Kuraev, G.T., 1981. Sarcocystis infection in dromedaries and bactrian camels in Kazakhstan. Veterinariya (Moscow), 7 : 4 1 - - 4 2 and in 1982 Vet. BulL, 52: 1707. Leek, R.G. and Fayer, R., 1978. Infectivity of Sarcocystis in beef products from a retail food store. Proc. Helminthol. Soc. Wash., 45: 135--136. Markus, M.B., Killik-Kendrik, R. and Garnharn, P.C.C., 1974. The coccidial nature and life cycle of 8arcocystis. J. Trop. Med. Hyg., 77: 248--259. Melhorn, H., Becker, B. and Heydorn, A.O., 1978. Light and electron microscopial studies on experiments producing gamagony of 5 Sarcocystis species in vivo and in tissue cultures. 2nd German--Japanese Cooperative Symposium on Protozoon Diseases, Bonn 31 Aug.--1 Sept. Quiroga, D., Lombardero, O. and Zorrilla, R., 1969. Sarcocystis tilopodi N sp. en guanacos (Lama guanicoe) de la Repdblica Argentina. Gac. Vet., 31 : 67--70.
101 Rioseco, H.M., Cubillos, G.V., Gonzalez, A.H. and Diaz, C.L., 1976. Sarcosporidiosis en puddes (Cervidae). Primer reporte en Chile. Arch. Med. Vet. (Chile), 8: 122-123. Rommel, M., Heydorn, A.O. and Gruber, F., 1972. Contribution to the life-cycle of the Sarcosporidea. I. The sporocyst of S. teneUa in the faeces o f cats. Berl. Muench. Tieraerztl. Wochenschr., 85: 101--104. Rommel, M., Heydorn, A.O. and Ether, M., 1979. The sarcosporidea of domestic animals and o f man. Berl. Muench. Tieraerztl. Wochenschr., 92: 457--464. Stalheim, H.V., Fayer, R. and Hubbert, W.T., 1980. Up-date on bovine toxoplasmosis and sarcocystosis with emphasis on their role in bovine abortion. J. Am. Vet. Med. Assoc., 176: 299--302. Tongson, M.S. and Pablo, L.S.M., 1979. Preliminary screening of the possible definitive hosts of Sarcocystis sp. found in Philippine buffaloes (Bubalus bubalis). Philip. J. Vet. Med., 18: 42--54.
95
SARCOCYSTIS SP. IN GUANACO (LAMA GUANICOE) AND EFFECT OF TEMPERATURE ON ITS VIABILITY
T.R. G O R M A N ,
H.A. A L C A i N O
and H. M U i ~ O Z
University o f Chile, School o f Veterinary Medicine, Casilla 49 Correo 15, La Granja, Santiago (Chile) C. CUNAZZA
Ministry o f Agriculture, C.O.N.A.F., Casilla 1237, Punta Arenas (Chile) (Accepted for publication 19 October 1983)
ABSTRACT Gorman, T.R., Alcaino, H.A., Mufioz, H. and Cunazza, C., 1984. Sarcocystis sp. in guanaco (Lama guanicoe) and effect of temperature on its viability. Vet. Parasitol., 15: 95--101. The biology of the Sarcocystis sp. that infect guanacoes was studied by feeding the infected meat to dogs, cats, rats and mice. Tissues from guanaco, heavily infected with macrocysts, were fed to these animals and their faeces collected daily and examined for the presence or absence of sporocysts. It was shown that only dogs were suitable definitive hosts. The effect of cooking and freezing on the viability of this protozoan organism was also investigated. Freezing to -18°C and -24°C and cooking were effective for inactivating Sarcocystis in guanaco meat. These methods could therefore be used instead of condemning guanaco carcasses infected with Sarcocystis.
INTRODUCTION
The study of the genus Sarcocystis has been stimulated by the discovery of its coccidian nature and its heterogeneous cycle involving carnivores as definitive hosts and herbivores as intermediate hosts (Fayer, 1972; Heydorn and Rommel, 1972; R o m m e l et al., 1972). There is now much information about the identificationof new hosts and species,characteristics of their life-cycle,importance of acute infections, and also economical impact of naturally- and experimentally-infectedanimals (Markus et al., 1974; Dubey, 1976; Melhorn et al., 1978; R o m m e l et al.,1979; Stalheim et al.,1980; Boch et al.,1980; Erber and Burgkart, 1981). The parasite has been identified in the muscles of wild herbivores, as well as in domestic-animal species, and the life~ycle has been investigated through experimental inoculation of possible definitive hosts (Emnett and Hugghins, 1979; Tongson and Pablo~ 1979; Dubey, 1980a, b; Collins, 1981; Kuraev, 1981). 0304-4017/84/$03.00
© 1984 Elsevier Science Publishers B.V.
96 Sarcosporidiosis in Chile is prevalent in domestic-animal species (Gorman et al., 1981), and is usually present as microscopic cysts which are n o t detected by routine inspection at abattoirs. The infection has also been reported frequently in alpaca (Lama pacos), guanaco (Lama guanicoe) (Cunazza, 1980), and p u d u (Pudu pudu) (Rioseco et al., 1976), b u t in these species it is generally present as macroscopic cysts, easily seen by the naked eye. Information obtained by officers of the Corporaci6n Nacional Forestal (CONAF), Ministry o f Agriculture, has led to the recognition of the infection as a problem in guanacoes, of the austral region of Chile. Serious efforts to encourage the breeding of this autochthonous species of mammal are being carried o u t in that region, since sheep farming has c o m p e t e d with and displaced guanaco from many areas of its natural environment. Sarcosporidiosis presents an economic problem, since its macroscopic appearance leads to rejection of some tissues and in severe cases to rejection of the whole carcass. It is n o t known whether Sarcocystis of guanaco can produce h u m a n infection. This study was undertaken to investigate some biological aspects and possible definitive hosts of the Sarcocystis of guanaco, as well as the effect of freezing and cooking on the viability of this protozoan. Heat treatment o f infected meat could prevent its rejection and thus encourage the breeding and commercial management o f the guanaco. MATERIALS AND METHODS In a preliminary study it was determined that dogs excreted sporocysts after ingesting guanaco meat infected with sarcocysts. In this study, dogs, cats, rats and mice were investigated as hosts through feeding experiments with meat infected with abundant visible cysts of Sarcocystis. Apart from the dogs, all the animals were raised in a laboratory and had n o t ingested meat before. Dogs were obtained through private dealers and they were kept in quarantine for 4 months before the experiments were started. During this period the dogs were treated with anthelmintics and an antiprotozoan p r o d u c t (Tinidazol 50 mg kg -1, twice a day for 7 days) to remove residual infections. Dogs and cats were housed in individual cages, and coprological examinations were performed dally on each of them for a period of 2 months before ingestion of the infected meat. A flotation technique with zinc sulphate solution was used. Eight rats and 8 mice were each infected with 3 macroscopic cysts of Sarcocystis from infected guanaco meat. F o u r dogs and 4 cats were fed daily 250 g and 50 g, respectively, of the infected meat for 5 days. Another cat and dog received dally 4 dissected macroscopic cysts each, for 4 days. The second experiment was c o n d u c t e d to determine whether Sarcocystis remained infectious after cooking or freezing.
97
In this study 13 dogs were used as follows: Group 1, uninfected controls -- 2 dogs that were fed only commercial food; Group 2, infected controls -- 5 dogs that were fed daily on 250 g of guanaco meat infected with Sarcocystis for 5 days; Groups 3, 4, 5, each group contained 2 dogs, each dog was fed daily on 250 g of infected guanaco meat for 5 days. The meat had been kept for 5 days at - 1 8 ° C or - 2 4 ° C , or had been c o o k e d above 60°C. In both experiments dogs' and cats' faeces were individually examined every day for 30 days, beginning on the day of the first feeding. When sporocysts were present, the period was extended for 90 days. Rats and mice were evaluated through daffy examination of pooled samples. The number of sporocysts was recorded and their average size was determined through 50 measurements in each infected animal. The prolonged effect of refrigeration was also studied b y feeding infected meat, refrigerated for 30 days, to a dog. RESULTS
Cats, rats and mice remained negative to the presence of sporocysts for as long as 30 days after the ingestion of Sarcocystis-infected guanaco meat. The 4 dogs that had ingested the infected meat, excreted sporocysts after a pre-patency of 9--16 days (:~ = 12; S.D. = 2.5) (Table I). The dog which was fed the macrocysts also became infected. The patent period varied between 19 and 61 days with an average of 45.6 days (S.D. = 16.7) (Table I).
TABLE I Pre-patent and patent period of Sarcocystis sp. from guanaco in experimentally-infected
dogs No. o f days Pre-patent
Patent
Dog No. 1 2 3 4 5a
9 12 12 11 16
61 58 42 48 19
S.D.
12.0 2.5
45.6 16.7
aInfeeted with dissected macroscopic cysts.
98
The number of sporocysts excreted varied throughout the elimination phase. The shedding~urve of sporocysts from 4 dogs is shown in Fig. 1. Average size of sporocysts were 14.6/~ long X 10.6/~ wide (S.D. = 0.41 and 0.58, respectively).
3r
--
Dog 1
--- Dog 2
2 ~
rl
; IV
~l
eo
,;
0 L 0
~
\./
!i
A
'\,
v
'/
AL~,1~. ' ',
•
',
V
L
A
'"
a
:
",_l__J." --
Dog 3
---
Dog 4
;. i
20
,,t
;\
'
10
,~
v\x.\ A
"i
al
z
,
30
40
Days
after
50
t
60
feeding
Fig. 1. Excretion of sporocysts by 4 dogs fed guanaco meat infected with Sarcocystis. No. o f sporocysts/g of faeces expressed as Log + 1.
The second experiment demonstrated that dogs fed either cooked or frozen meat infected with Sarcocystis, did not excrete sporocysts for the 30-day observation period. However, control dogs that had ingested refrigerated meat, became infected with the parasite since they shed sporocysts. The dog fed the meat that had been refrigerated for 30 days also excreted sporocysts. It was found that dogs receiving only commercially prepared pelleted food, did not excrete sporocysts during the 30-day observation period (uninfected controls). DISCUSSION
Of the species studied, only dogs proved to be suitable definitive hosts for the 8arcocystis species that infect guanacoes. The choice of species screened as possible definitive hosts was based on the existence of similar
99
and related species in the guanaco environment, in the austral region of Chile. Foxes and wild dogs are abundant in this region. F r o m our results it is natural to presume that under natural conditions of the guanaco habitat, these species of carnivores m a y play an important role in the lifecycle o f Sarcocystis. It would be interesting to study the relationship of other wild carnivores such as prey- or carrion~ating birds (condors) that may act as predators on guanacoes. On the other hand, since cats did n o t become infected it is possible that wild felids such as the p u m a are n o t suitable hosts for this Sarcocystis sp. It is therefore recommended that further studies involving these species should be carried out. As the protozoan organisms were present as macroscopic and microscopic cysts, it was assumed that there could exist a difference o f infectivity among the 2 forms. However, by feeding dissected macroscopic cysts to 1 dog (No. 5) and 1 cat, it was observed that both forms were infective to dogs, b u t n o t to cats. The amount o f sporocysts excreted by the infected dogs was variable although a peak was observed around the 18th and 31st day post-infection. After 36 days their number started to decline and no special pattern of variation was observed as reported previously (Fig. 1) (Fayer, 1977; E m n e t t and Hugghins, 1982). Freezing and cooking seem to be suitable methods for destroying the protozoan organisms in the meat. However, refrigeration temperatures of 5°C, did n o t affect their viability. In addition, it was observed that prolonged refrigeration, for 30 days, was quite ineffective in destroying the organisms since a dog fed with such treated meat excreted sporocysts. Extraneous and accidental infections with organisms during the experiment were ruled out, since the dogs fed only pelleted food did n o t have any sporocysts u p o n coprological examinations throughout the experiment. These findings are in agreement with those reported by Gestrich and H e y d o r n (1974), Fayer (1975), and Leek and Fayer (1978), in that cooking and freezing are effective methods for inactivating this protozoa. It is n o t known yet whether Sarcocystis-infected guanaco meat might induce human infections. These treatments of the meat present a means for salvaging guanaco meat which would otherwise be destroyed due to sarcosporidiosis, and hence a motivation to breed guanaco as a productive species. With regard to the name of this Sarcocystis species, Quiroga et al. proposed in 1969 the name S. tilopodi for the p r o t o z o a in guanacoes. Although no studies have been done on infection of guanacoes with sporocysts excreted by dogs, the new trends in nomenclature would indicate that a suitable name would be S. guanicoe-canis in order to distinguish it from S. lama-canis in animals o f the Lama genus.
100 ACKNOWLEDGEMENTS
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