Assessment of the diagnostic performance of four methods for the detection of Giardia duodenalis in fecal samples from human, canine and feline carriers

Abstract

Enteric parasitic diseases including giardiasis are of public health concern. Different methods are available for the diagnosis of this parasitic infection in fecal samples such as the identification of protozoan cysts and trophozoites by light microscopy, detection of specific antigens by ELISA, and amplification of DNA fragments by PCR. The present study aimed at assessing the performance of four laboratory tests for the detection of Giardia duodenalis in fecal specimens from three different host species with a previous diagnosis of giardiasis; canine, feline and human patients provided new stool samples to be retested for Giardia before initiating treatment with antiprotozoal drugs. For this purpose, triplicate fecal specimens from 54 humans, 24 dogs and 18 cats living in the city of Niterói, RJ, southeast Brazil, were analysed by light microscopy, ELISA, immunochromatography, and nested PCR. The centrifugal-flotation method detected Giardia cysts in 89.6% (86/96) of the fecal samples. The protozoan parasite was detected via immunochromatography in 87.5% (84/96) of these samples. Giardia was detected by ELISA in 69.8% (67/96) of the stool specimens from carriers with a previous diagnosis of Giardia infection. Giardia was detected by PCR in only 39.6% (38/96) of the fecal specimens. Based on these findings, we suggest that, among the four assays that were used in this study, the zinc sulphate flotation technique (Faust et al., 1939) is the best diagnostic assay in terms of sensitivity and specificity to detect G. duodenalis on serially collected samples from dogs, cats and humans.

Rapid on-site diagnosis of canine giardiosis: time versus performance

“…Based on the above, it is evident that a single negative result may not definitely determine the presence or absence of Giardia spp. in examined dogs and therefore re-examination of fecal samples is necessary to increase the sensitivity of the method [ 48 , 70 , 71 ]. The demand for repeated testing renders microscopy a time-consuming and labor-strenuous method.…”

Retrospective and Comparative Study of Giardia sp. Prevalence in Dogs, Cats, and Small Ruminants in Endemic Areas in Different Brazilian States

“…Essa possibilidade também pode ser considerada para as outras espécies, pois o padrão de eliminação intermitente de cistos de Giardia sp. nas fezes e o baixo número de cistos são pontos relevantes no diagnóstico, tornando-o um desafio [60].…”

“…Amostras em triplicata podem aumentar a sensibilidade da técnica de centrifugo-flutuação em sulfato de zinco, padrão-ouro para o diagnóstico de Giardia [41,60]. No entanto, as amostras únicas deste estudo forneceram resultados satisfatórios em relação a sensibilidade e prevalência para detecção de cistos de Giardia sp.…”

“…Amostras de fezes sabidamente positivas e testadas novamente pela técnica de centrifugo-flutuação em sulfato de zinco, em três coletas diferentes, apresentam maior positividade (89,6%) se comparadas as demais técnicas disponíveis para o diagnóstico das infecções por Giardia sp. (imunocromatografia, ELISA e PCR -representando 87,5%, 69,78% e 39,6%, respectivamente) [60], justificando a escolha desta técnica para o diagnóstico e realização deste estudo.…”

Comparative cost-effectiveness of immunoassays and FLOTAC for diagnosing Giardia spp. infection in dogs

“…However, some animals do not present any clinical signs [10]. Surveys on a variety of canine populations have revealed a prevalence of Giardia infection ranging from 10% among well-cared-for dogs to 36–50% among puppies and up to 100% among kennel dogs, which are at highest risk of disease transmission [11]. Many factors appear to affect the prevalence of the infection including the animal’s characteristics (age, living conditions, animal density, nutritional status and immune status) and the diagnostic test used [12].…”