Parasitol Res DOI 10.1007/s00436-012-3096-2

SHORT COMMUNICATION

Subacute and acute fasciolosis in sheep in southern Brazil Leticia Fiss & Maria de Lourdes Adrien & Clairton Marcolongo-Pereira & Nathalia D. Assis-Brasil & Eliza S. V. Sallis & Franklin Riet-Correa & Jerônimo L. Ruas & Ana Lucia Schild

Received: 25 July 2012 / Accepted: 21 August 2012 # Springer-Verlag 2012

Abstract Eight outbreaks of acute and subacute fasciolosis are reported in sheep in the municipality of Santa Vitória do Palmar, southern Brazil, in areas used for irrigated rice cultivation, which are subject to frequent flooding. Two outbreaks occurred mid-winter during July and August, and six occurred during spring and early summer. Morbidity ranged from 3 to 66.7 %, and mortality ranged from 3 to 50 %. Clinical signs included weight loss, mucosal pallor, apathy, depression, muscle tremors, and drooling; these were followed by death within approximately 24 h. Some sheep were found dead. Gross lesions were characterized by an irregular liver capsule with fibrin deposition L. Fiss : M. de Lourdes Adrien : C. Marcolongo-Pereira : N. D. Assis-Brasil Programa de Pós-Graduação em Veterinária, Laboratório Regional de Diagnóstico—Faculdade de Veterinária, Universidade Federal de Pelotas, Pelotas, RS, Brazil E. S. V. Sallis Departamento de Patologia Animal—Faculdade de Veterinária, Universidade Federal de Pelotas, Campus Universitário s/n, 96010-900 Pelotas, RS, Brazil J. L. Ruas : A. L. Schild (*) Laboratório Regional de Diagnóstico—Faculdade de Veterinária, Universidade Federal de Pelotas, Campus Universitário s/n, 96010-900 Pelotas, RS, Brazil e-mail: [email protected] F. Riet-Correa Veterinary Hospital, CSTR, Universidade Federal de Campina Grande, Campus de Patos, 58700-000 Patos, PB, Brazil

and hemorrhages. The liver parenchyma contained hemorrhagic tracts or irregular clear areas alternated with dark hemorrhagic areas. Histologically, hemorrhagic dark red tracts of necrotic liver parenchyma and an inflammatory infiltrate were noted; these lesions coincided with the presence of immature flukes. Langhans-type giant cells, fibrous tissue, and bile duct cell proliferation were observed in subacute cases. Chronic fasciolosis is a well-known disease to farmers in southern Brazil; nevertheless, acute and subacute fasciolosis, which are more difficult to diagnose and treat, may cause important economic losses. Efficient control of fasciolosis requires integration of measures to treat infections in the definitive host, to reduce the population of snails of the genus Lymnaea, and to avoid contact between the parasite and host by appropriate pasture management.

Fasciola hepatica is the most common liver fluke and a parasitic zoonosis. This parasite affects ruminants and numerous other mammalian species in several countries throughout Europe, Asia, and America (Gajewska et al. 2005; Radostits et al. 2007). Parasitic spread correlates with the presence of snails of the genus Lymnaea, which function as the intermediate host; sheep and cattle are the definitive hosts and serve to disseminate eggs. The economic losses associated with fasciolosis are primarily a result of decreased weight gain, decreased milk and wool production, interference with fertility, costs associated with treatment, and condemnation of affected livers at slaughterhouses (Gajewska et al. 2005). Death can occur in animals with severe infections (Pullan and Whitten 1972). In Brazil, the highest prevalence of fasciolosis is found in the southern region and in the states of São Paulo, Minas Gerais, Rio de Janeiro, and Goiás (Cunha et al. 2007). The

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disease is endemic in Rio Grande do Sul, especially in the south and southeast parts of the state; in the southeast, the Patos, Mirim, and Mangueira Lakes and the flat wetlands used to irrigated rice fields contribute to the dissemination and maintenance of flukes year-round (Cunha et al. 2007). In Brazil, three species of Lymnaea have been reported: Lymnaea columella in Rio de Janeiro, São Paulo, Minas Gerais, Santa Catarina, and Rio Grande do Sul; Lymnaea cubensis in Rio de Janeiro; and Lymnaea viatrix in Rio Grande do Sul (Echevarria 2004). In the municipality of Santa Vitória, the only species reported is L. viatrix (Müller 2007). Depending on the number of ingested metacercariae, fasciolosis can present in a subclinical, acute, subacute, or chronic form. The acute and subacute forms are primarily due to mechanical damage caused by the simultaneous migration of more than 1,000 immature flukes in the hepatic parenchyma (Boray 1967; Brunsdon 1967; Müller 2007). The chronic form develops when the adult parasites migrate to the bile duct, where they cause cholangitis, biliary obstruction, and fibrosis (Radostits et al. 2007). Experimental trials have demonstrated that 400–500 metacercariae are required to produce chronic fasciolosis in sheep (Rushton and Murray 1977; Boyce et al. 1987). At approximately 5 weeks post-infection, the lesions are similar to those of acute fascioliasis; however, the functional reserves of the liver are sufficient to avoid death (Sewell 1966; Rushton and Murray 1977). In cases of acute fasciolosis, sheep do not usually succumb to their disease before week 7 or 8 of infection; at this stage, approximately 60 % of flukes are migrating in the left liver lobe (Brunsdon 1967; Dow et al. 1968). To control the disease, triclabendazole has been the most effective flukicide against early immature and adult flukes (Boray 1967). This drug causes a reduction in the concentration of circulating antigens 2–4 weeks after treatment in naturally infected sheep (Sanchéz-Andrade et al. 2001). The aim of this paper is to report the epidemiology, clinical

Table 1 Epidemiology of acute/ subacute fasciolosis outbreaks diagnosed in Santa Vitória do Palmar, southern Brazil, 1980–2011

signs, and pathology of acute and subacute fasciolosis outbreaks in the sheep of southern Brazil. All outbreaks occurred in the municipality of Santa Vitória do Palmar, located in southern Rio Grande do Sul State (latitude south between 32°40′01.02″ and 33°31′ 21.79″; longitude west between 52°37′01.99″ and 53°24′ 52.35″), where chronic fasciolosis is endemic (Müller 2007). This region is used primarily to cultivate irrigated rice and raise sheep and cattle. The water is pumped from Lagoa Mirim to rice fields through irrigation channels, which provide an ideal environment for the intermediate host; moreover, frequent flooding of the paddocks favors the spread and maintenance of the snails throughout the year (Müller et al. 1999). The disease affected primarily adult sheep. Morbidity ranged from 3 to 66.7 %, and mortality ranged from 3 to 50 %. Six outbreaks occurred from September to January (spring and early summer) and two in July and August (winter). Some epidemiological data of the outbreaks are presented in Table 1. In outbreak #3, the flock was treated with Ranide® (rafoxanide 3 % and 2.7 % albendazole) after the occurrence of the first deaths, but sheep continued to die 3 days after treatment. In outbreak #7, sheep were treated with Ripercol® (levamizol 5 %) 20 days before mortality. In outbreak #8, the affected lambs were weaned and placed in a rice stubble without anthelmintic treatment; 5–6 months later, 14 lambs died in a 20-day period. After the first deaths in mid-November, the lambs were treated with two dosages of Dovenix Supra® (nitroxynil 34 %) at a 20-day interval. After the second treatment, the animals were removed from the paddock. Six other lambs died after removal. After the diagnosis of the other outbreaks, the disease was controlled by treatment with Dovenix Supra® and removal of flocks from the paddocks. Clinical signs included weight loss, mucosal pallor, apathy, depression, muscle tremors, and drooling; these were followed by death within approximately 24 h. Some sheep

Outbreak

Month/year

Animals at risk

Category

Morbidity (%)

Mortality (%)

1 2 3 4 5 6 7 8

August 1980 November 1980 December 1980 January 1982 January 1985 September 1994 July 2007 December 2011

250 300 500 3,000 400 154 63 230 4,897

Not available Adult Adult Not available Adult/lambs Adult Adult Lambs

36 13.34 20 3 50 11.7 66.7 8.7 12.25

36 6.67 14 3 50 11.7 33.3 8.7 10.8

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Fig. 1 Visible red areas in the cut sections of the liver parenchyma (a). Young forms of F. hepatica migrating in the hepatic parenchyma (b)

were found dead. None of the nine fecal samples from necropsied sheep contained F. hepatica eggs. Gross lesions in acute fasciolosis were characterized by a slightly irregular liver surface covered by fibrinous exudates, dark red areas of hemorrhage, and fibrin deposition. Many randomly distributed red areas of 0.5 to 5 mm were visible in cut sections of the liver parenchyma (Fig. 1a). Histologically, there was extensive liver damage characterized by hemorrhagic dark red tracts of necrotic liver parenchyma and an inflammatory infiltrate composed mainly of eosinophils. Young forms of F. hepatica migrating in the hepatic parenchyma were observed (Fig. 1b). In subacute cases, the capsular surface of the liver was hemorrhagic with the presence of fibrin. Depressed and tortuous dark areas were observed in some cases (Fig. 2a). The cut surface of the liver was irregular, with clear areas alternated with dark hemorrhagic areas (Fig. 2b). Some sheep had ascites, and immature forms of F. hepatica were found to be migrating into the hepatic parenchyma. Histologically, the liver of subacute cases revealed hemorrhagic areas surrounded by degenerated hepatocytes and infiltrated by inflammatory cells including eosinophils and

Fig. 2 Hemorrhagic capsular surface of the liver with the presence of fibrin (a). The cut surface of the liver is irregular, with clear areas alternated with dark hemorrhagic areas

neutrophils (Fig. 3a, b). Macrophages containing hemosiderin were observed. In some cases, the bile ducts presented hyperplasia of the epithelial cells and fibrosis (Fig. 4a). In tracts where parasites had migrated, there was a central eosinophilic core with cellular debris and necrotic hepatocytes; this core was surrounded by macrophages and Langhans-type giant cells (Fig. 4b). Thrombi with eosinophils were observed in the portal vein, the central vein, and the hepatic artery. Infiltration by lymphocytes and plasma cells was also observed in some areas. The diagnosis of subacute and acute fasciolosis was based on the pathology observed in necropsied sheep from the affected flocks. Extensive liver damage, hemorrhagic dark red tracts of necrotic liver parenchyma, and the presence of immature flukes are a characteristic of acute fasciolosis between the fourth and sixth weeks post-infection (Dow et al. 1968). The presence of macrophages, Langhans-type giant cells, and fibrous tissue indicates subacute disease, which occurs between 6 and 10 weeks after

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Fig. 3 a, b The liver of subacute cases revealed hemorrhagic areas surrounded by degenerated hepatocytes and infiltrated by inflammatory cells including eosinophils and neutrophils

infection (Boray 1967; Dow et al. 1968). In Brazil, this region has the highest percentage of liver condemnation by fasciolosis at slaughterhouses, ranging from 18.6 % (Dutra et al. 2010) to 19.6 % (Cunha et al. 2007) in cattle and from 9 to 11 % in sheep (Ueno et al. 1982; Cunha et al. 2007). Acute fasciolosis has not been reported previously in Brazil. In a report of the prevalence of F. hepatica infections at slaughterhouses in southern Brazil, Ueno et al. (1982) mentioned the possible occurrence of acute fasciolosis between July and November with a mortality rate of 15–20 %. In the present study, acute fasciolosis occurred between July (mid-winter) and January (start of summer); mortality ranged from 3 to 50 %, and morbidity ranged from 3 to 66.7 %. Due to the presence of acute or hyperacute clinical signs and the absence of F. hepatica eggs in the feces, acute fasciolosis should be diagnosed by the typical gross and histologic findings and the presence of immature F. hepatica in the liver parenchyma. Experimental infections with 4,000 or more metacercariae produce fatal acute or subacute disease with deaths occurring 8–10 weeks post-infection (Boray 1967). With regional temperatures below 10 °C

Fig. 4 Hyperplasia of the epithelial cells of the bile ducts and fibrosis (a). In tracts where parasites had migrated, there is a central eosinophilic core with cellular debris and necrotic hepatocytes, surrounded by macrophages and Langhans-type giant cells (b)

during winter (June to September), outbreaks 1 and 7 most likely occurred due to ingestion of metacercariae that overwintered in the pastures after the liberation of cercariae from the snails in late autumn. Outbreaks 2, 3, 4, 5, 6, and 8 were most likely due to the liberation of cercariae from the snails in early spring or late autumn. In similar areas of Uruguay, the number of cercariae liberated from Lymnaea spp. was reported to increase considerably in the early spring due to the reactivation of the cycle that was stopped or delayed during winter (Acosta 1994). In endemic regions such as southern Rio Grande do Sul, chronic fasciolosis is well-known to farmers and veterinarians who control the disease efficiently. Nevertheless, acute and subacute disease may cause important economic losses. The efficient control of fasciolosis requires the integration of measures to reduce infections in the definitive hosts by treatment with fasciolicides, to minimize the population of Lymnaea snails, and to avoid contact between the parasite and host using pasture management.

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