Mycobacterium gordonae infection in freshwater fish from lakes and ponds in a park at Sao Paulo city, Brazil
Abstract
In recent year’s fish farming has greatly increased in Brazil, favoring the development of diseases such as mycobacteriosis. This is a chronic progressive disease that affects temperate and tropical fish, both freshwater and marine. Mycobacteriosis can occur in several species of fish and amphibian. In addition, some species of Mycobacterium spp. can be transmitted to humans by occupational or recreational source. A total of 54 fishes from lakes from São Paulo city, were collected and examined for mycobacteriosis. Granulomas were visualized in 5 fishes via histopathology (H&E), and acid - alcohol resistant bacilli were visualized in 8 animals by electron microscopy and 8 were positives using the Fite-Faraco technique. In this study, we isolated acid-fast bacillus from one fish which were identified as M. gordonae by molecular methods: PCR and sequencing.
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Introduction
In recent years fish farming has greatly increased in Brazil, favoring the development of diseases such as mycobacteriosis (ISHIKAWA et al., 2001; ROMANO et al., 2012). This is a chronic progressive disease that affects temperate and tropical fish, both freshwater and marine (JACOBS et al., 2009).
Mycobacteria spp. can cause serious and costly diseases in different vertebrates and invertebrates, such as humans (tuberculosis, leprosy, Buruli ulcer), livestock (bovine tuberculosis) and ectotherms (reptiles, amphibians and fish) (BIET et al., 2005; GRANGE & YATES, 1986; JACOBS et al., 2009; REAVILL & SCHMIDT, 2012; SHINNICK & GOOD, 1994; TORTOLI, 2003; TURENNE et al., 2007).
The first Mycobacterium spp. was identified in carp in 1897 (BATAILLON, DUBARD, TERRE, 1897). This was named as Mycobacterium piscium and was shown to be highly pathogenic to frogs and some endothermic animals. The main species identified in captive and wild fishes are M. marinum, M. fortuitum and M. chelonae (mainly in marine fish). New species have also been proposed, including M. salmoniphilum. Other organisms related to M. ulcerans and the M. tuberculosis complex have also been recently implicated (GAUTHIER & RHODES, 2009; JACOBS et al., 2009).
Transmission typically occurs by ingestion of contaminated food and water, but transovarian transmission can also occur in viviparous species (ASTROFSKY et al., 2000; GAUTHIER & RHODE S, 2009; JACOBS et al., 2009).
Granulomas are mainly located in the spleen, liver and kidney during the initial stages of the disease, but can spread to any other organs, leading to terminal illness. At the beginning of the infection, macrophages are invaded and become epithelioid cells. Giant cells may or not be present (GAUTHIER & RHODES, 2009; JACOBS etal., 2009).
In fish, the severity of mycobacteriosis ranges from chronic infection, without major changes in tissues and few losses, to severe and acute infection, with high mortality, depending on the mycobacteria and fish species involved. Clinical signs include weight loss, apathy and lethargy, decreased fertility spine defects, exophthalmia, abnormal behavioral, changes in skin color, and ulcerativele sions in the skin, gills, fins and musculature. There may be enlargement of liver, spleen, kidney and nodular lesions in internal organs (ASTROFSKY et al., 2000; GAUTHIER & RHODES, 2009; JACOBS et al., 2009; ROMANO et al., 2012).
There are few reports of mycobacteriosis in fish and amphibian species in Brazil. Studies are needed to understand the occurrence and consequences of the disease in animals maintained in captivity in lakes, ponds and parks (FERREIRA et al., 2006; ISHIKAWA et al., 2001; LEITE et al ., 1998; ROMANO et al., 2012).
The aim of this study was to study this disease of fishes in the lakes and ponds park in São Paulo city and from decorative lake, unfit for consumption.
Conclusion
Brazil has enormous potential for animal and fish farming production, given its vast land, water sources and favorable weather conditions. In Brazil, fish are typically raised in lakes for consumption, although in this study they were not intended for consumption.
High concentrations of fish can favor the onset epizootic disease outbreaks caused by Mycobacteria spp, although in natural environmental conditions spontaneous disease outbreaks can also occur (GAUTHIER & RHODES, 2009; HECKERT et al., 2001; RAMSAY et al., 2009).
Mycobacteriosis can occur in several species of fish. In addition, some species of Mycobacterium spp. can be transmitted to humans by occupational or recreational source (BHATTY et al., 2000; GAUTHIER & RHODES, 2009; JACOBS et al., 2009; REAVILL & SCHMIDT, 2012).
In Brazil, there are a few studies on mycobacteriosis in ectotherms. MOK and CARVALHO in 1984, described the presence of M. chelonei in Bufus marinus and B. granulosus, and although mycobacteriosis outbreaks in frog farms have been reported by FERREIRA et al., 2006. In fish, was notification by ISHIKAWA et al., 2001 and ROMANO et al., 2012.
Histopathological examinations are important for early diagnosis of mycobacterial infection in fish. Granulomas are suggestive of mycobacteriosis but are not pathognomonic of the disease; acid –fast bacilli must be visualized in the lesions. A positive culture will provide a definitive diagnosis, but it is not very easy to isolate mycobacterias at 37° C, the optimum temperature for human pathogens. Fishes isolate are well-characterized by molecular methods.
In this study, we isolated acid-fast bacillus from one fish which were identified as M. gordonae by molecular methods. It is recommended that further, more in-depth, studies are undertaken to gain a better insight of the impact of this disease in cultured and wild fish species in Brazil.