A large scale molecular study of Giardia duodenalis in horses from Colombia
Introduction
Giardia duodenalis (syn. G. lamblia, G. intestinalis) is a widespread intestinal parasite of mammals. Molecular characterization has identified seven major assemblages (A–G) of G. duodenalis that appear to have different host ranges. Additional genotypes have been reported in mammals, genotype H in seals and the quenda genotype in quenda and cattle (Adams et al., 2004, Lasek-Nesselquist et al., 2010, Ng et al., 2011). Giardia was first reported as a parasite of horses in South Africa in 1921 (Fantham, 1921). Although it has been found in horses with diarrhea (Manahan, 1970, Kirkpatrick and Skand, 1985), infected horses rarely show any clinical signs (Bemrick, 1968) and no subclinical effects have been reported. Nearly all reports of giardiasis in equines are based on microscopic studies in which cysts were observed in feces (Fantham, 1921, Bemrick, 1968, Kirkpatrick and Skand, 1985, Manahan, 1970, Xiao and Herd, 1994, Pavlásek et al., 1995, Olson et al., 1997, Johnson et al., 1997, Rigolon and Vargas, 1998, Atwill et al., 2000). Recently, G. duodenalis Assemblages A, B, and E have been detected in horses (Traub et al., 2005, Veronesi et al., 2010). Because Assemblages A and B are known to infect humans (Monis et al., 1999, Thompson, 2004) horses could represent a reservoir of G. duodenalis with the potential to cause disease in humans through direct contact or by contamination of food and water supplies. Although molecular methods have recently been applied to determine the prevalence of G. duodenalis assemblages in some domesticated and companion animals (Feng and Xiao, 2011), information regarding the prevalence of G. duodenalis in horses has been limited to a very small number of animals (Traub et al., 2005, Veronesi et al., 2010, Traversa et al., 2012). Therefore, the present study was undertaken to determine the prevalence of G. duodenalis in a large number of horses, to determine the assemblages present, and to determine any age and gender related preferences in the prevalence of infection.
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Animals and collection of specimens
In 2008 fecal specimens were collected from 195 horses in four regions in Colombia: 60 from Sabana de Bogotá (Region A), 60 from Costa Atlántica (Region B), 50 from Llanos Orientales (Region C), and 25 from Bogotá D.C. (Region D) (Table 1). Region A horses are “Silla Argentino” breed. Males are housed in separate stables and their drinking water is from the nearest municipally aqueduct while females are pastured with colts with access to natural spring water. Region B horses are “Paso fino
Prevalence
Of fecal specimens obtained from 195 horses 34 (17.4%) were PCR positive based on ssurRNA (Table 1). For horses from regions A, B, C, and D, 3.3%, 23.3%, 24%, and 24% of the specimens were found PCR positive for G. duodenalis, respectively. These included 11 male and 23 female horses that ranged in age from 2 months to 13 years (Table 2). Prevalence of infection based on gender differences was not significant (p = 0.5624). Prevalence of infection based on age differences was also not significant (
Discussion
The results confirmed the presence of G. duodenalis in horses from Colombia for the first time. Diarrhea was not observed in any of the specimens in the present study and solid evidence for Giardia as a cause of illness in horses is scant. Giardia infection was believed responsible for chronic diarrhea, weight loss, lethargy, inappetence, and dermatitis in a 4-year-old Thoroughbred based on the finding of cysts in feces and the resolution of clinical signs after treatment with metronidazole (
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