Evaluation of the SNAP® 4Dx® plus test for the detection of Dirofilaria immitis antigen and characterization of exposure to tick-borne pathogens in wild canids in southern Ontario

[Overview on utility of in-house tests for detection of systemic infectious diseases in dogs]

For detection of infectious diseases, several point-of-care (POC) tests are on the market in addition to methods performed in commercial laboratories. These POC tests are based on enzyme-linked immunosorbent assay (ELISA) or other immunochromatographic technologies and present results within few minutes in veterinary practice. This article gives an overview of the utility of numerous POC tests of different manufacturers for detection of parvovirus antigen in feces, Dirofilaria (D.) immitis antigen in blood as well as antibodies against Borrelia (B.) burgdorferi, Anaplasma (A.) spp., Ehrlichia (E.) spp., Leptospira (L.) spp. and Leishmania (L.) infantum in blood (single or in different combinations). Sensitivity and specificity of these tests are important for their usefulness in veterinary practice. Furthermore, presence of antibodies or detection of antigen has to correlate with the presence of clinical signs. POC tests for detection of canine parvovirus antigen have a very high specificity, the sensitivity of all evaluated POC tests, however, is very low. POC tests for detection of D. immitis antigen have a very high sensitivity and specificity. As they detect antigen from the uterus of female adult parasites, test results are negative when only very few female or only male adults are present. POC tests for detection of antibodies against B. burgdorferi only indicate contact with Borrelia spp. and do not prove clinical Lyme disease, as the infection only extremely rarely causes clinical signs. POC tests for detection of antibodies against A. phagocytophilum are also not suitable for diagnosis of clinical anaplasmosis. Infections with A. phagocytophilum only lead to clinical disease in very rare cases and in these, clinical signs occur before the development of antibodies. POC tests for detection of antibodies against E. canis have a very high sensitivity as well as specificity. POC tests for detection of antibodies against L. infantum and Leptospira species (spp.) show a very high specificity and a high sensitivity. However, Leptospira spp. antibody-positive results may occur following vaccination, as the POC tests cannot distinguish between field and vaccination strains.

Wildlife parasitology: sample collection and processing, diagnostic constraints, and methodological challenges in terrestrial carnivores

Wild terrestrial carnivores play a crucial role as reservoir, maintenance, and spillover hosts for a wide parasite variety. They may harbor, shed, and transmit zoonotic parasites and parasites of veterinary importance for domestic hosts. Although wild carnivores are globally distributed and comprise many different species, some living in close proximity to human settlements, only a few studies have investigated parasites of wild terrestrial carnivores using non-specific techniques. Access to samples of wild carnivores may be challenging as some species are protected, and others are secretive, possibly explaining the data paucity. Considering the importance of wild carnivores' health and ecological role, combined with the lack of specific diagnostic methodologies, this review aims to offer an overview of the diagnostic methods for parasite investigation in wild terrestrial carnivores, providing the precise techniques for collection and analysis of fecal, blood, and tissue samples, the environmental impact on said samples, and the limitations researchers currently face in analyzing samples of wild terrestrial carnivores. In addition, this paper offers some crucial information on how different environmental factors affect parasite detection postmortem and how insects can be used to estimate the time of death with a specific highlight on insect larvae. The paper contains a literature review of available procedures and emphasizes the need for diagnostic method standardization in wild terrestrial carnivores.

A retrospective serosurvey of selected pathogens in red foxes (Vulpes vulpes) in the Tuscany region, Italy

The expansion of urbanization in natural environments increases interactions between wildlife, domestic animals, and humans. In Italy, the red fox (Vulpes vulpes) is one of the most common wild carnivores. This species can serve as a reservoir and sentinel host for several infectious diseases. We aimed to improve knowledge about the exposure of red foxes to selected zoonotic (Anaplasma spp, Ehrlichia spp., Borrelia spp., and hepatitis E virus) and carnivore-specific pathogens (canine parvovirus, canine distemper virus, pseudorabies virus, and Dirofilaria spp.) through a retrospective survey performed in the Tuscany region during the spring season of 2013. Using specific ELISAs and serum samples (n = 38) collected during a culling campaign, a prevalence of 2.6% for canine distemper virus, 18.4% for canine parvovirus, 5.2% for Anaplasma spp., 2.6% for Ehrlichia spp., 7.9% for Dirofilaria spp., 21.05% for hepatitis E virus, and 10.5% for pseudorabies virus was observed. Conversely, antibodies against Borrelia spp. were not identified in any of the animals. Our results revealed no significant sex-related differences in seroprevalence and confirmed hepatitis E virus as the most common pathogen in the analyzed samples. All of the animals that tested positive for tick-borne zoonotic agents presented ticks at the time of sampling. Our study confirms the exposure of red foxes in the Tuscany region to viral and bacterial infections raising medical and veterinary concern and indicating the need for large-scale surveillance to fully assess the epidemiological significance of these findings.

Detection of Dirofilaria immitis via integrated serological and molecular analyses in coyotes from Texas, United States

Wild canids serve as reservoir for various vector-borne pathogens of veterinary and medical importance, including the canine heartworm, Dirofilaria immitis. In North and Central America, coyotes (Canis latrans) may be a relevant reservoir host for heartworm transmission. The objective of this study was to determine the occurrence of D. immitis in coyotes across Texas using integrated antigen detection test and molecular assays. Matching whole blood and serum samples were collected from 122 coyotes from different locations across the state of Texas, United States, encompassing nine counties. Collections occurred from February to April 2016, and December 2016. Samples were assessed serologically using a commercial microtiter plate ELISA (DiroCHEK®), and molecularly by conventional PCR targeting the cytochrome oxidase c subunit 1 (cox1) and NADH dehydrogenase subunit 5 (nad5) of the mitochondrial DNA, and via a TaqMan© probe-based real-time PCR protocol, also targeting a fragment of the cox1 gene. Overall, 12 (9.83%) samples tested positive when serological and molecular results were combined. Seven of 122 samples (5.73%) were antigen-positive, 8 (6.55%) were qPCR-positive, and 4 (3.27%) were positive using conventional PCR. Of 12 positive samples, 4 tested antigen-positive by DiroCHEK® but were negative in all molecular tests, another 4 tested positive by at least one of the molecular assays but tested negative by DiroCHEK®, and 3 samples tested positive by both antigen test and at least one of the molecular assays. Two samples (16.67%) tested positive on both the antigen test and both conventional PCR and qPCR. Our study confirmed the presence of D. immitis infection in coyotes from southern and northern Texas. The combination of serologic and molecular diagnostic tests was proven synergistic for the identification of D. immitis infections, including occult dirofilariosis, and revealed a more accurate picture of heartworm occurrence in the sampled coyotes.

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Coyotes are an important wild reservoir for Dirofilaria immitis in North America.

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We collected 121 matching blood and serum samples of coyotes from Texas, USA.

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Twelve samples (9.92%) tested positive combining serology and molecular tests data.

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Probe-based qPCR was superior than conventional PCR for heartworm diagnosis.

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Combined DiroCHEK® and qPCR data showed a higher prevalence than each test alone.

The Agreement between Feline Pancreatic Lipase Immunoreactivity and DGGR-Lipase Assay in Cats-Preliminary Results

Simple Summary

Feline pancreatitis is a common disease with diagnostics requiring a combination of clinical, laboratory and imaging methods. Measuring of pancreatic lipase concentration is the laboratory mainstay of feline pancreatitis diagnostics. It can be done using immunoenzymatic assay (feline pancreatic immunoreactivity, fPLI) or colorimetric assay based on hydrolyzing a special substrate (DGGR) to a color product. A DGGR-lipase assay is manufactured by various companies. Studies carried out in cats on the DGGR-lipase assay of a single manufacturer have shown a high agreement with fPLI, however studies in dogs indicate that the performance of assays of different manufacturers may vary considerably. One of the largest Polish veterinary laboratories working 24/7 in the largest Polish cities offers the DGGR-lipase assay of a large Polish laboratory solutions provider. The values obtained in this assay are higher than those yielded by the traditional DGGR-lipase assay validated in studies carried out so far. Therefore, we decided to evaluate the agreement between the DGGR-lipase assay of the Polish manufacturer and fPLI. The agreement proved to be as high as for the traditional assay.

Abstract

The colorimetric catalytic assay based on the use of 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6′-methylresorufin) (DGGR) ester as a substrate for pancreatic lipase activity is commonly used for the diagnosis of pancreatitis in dogs and cats. Even though the assay has generally been shown to yield consistent results with feline pancreatic lipase immunoreactivity (fPLI) assay, the agreement may vary between assays of different manufacturers. In this study, the chance-corrected agreement between a DGGR-lipase assay offered by one of the biggest providers of diagnostic solutions in Poland and fPLI assay was investigated. The study was carried out on 50 cats in which DGGR-lipase activity and fPLI were tested in the same blood sample. The chance-corrected agreement was determined using Gwet’s AC₁ coefficient separately for the fPLI assay’s cut-off values of >3.5 μg/L and >5.3 μg/L. The DGGR-lipase activity significantly positively correlated with fPLI (R_s = 0.665; CI 95%: 0.451, 0.807, p < 0.001). The chance-corrected agreement between the fPLI assay and DGGR-lipase assay differed considerably depending on the cut-off values of the DGGR-lipase assay. When the cut-off value reported in the literature (>26 U/L) was used, it was poor to fair. It was moderate at the cut-off value recommended by the laboratory (>45 U/L), and good at the cut-off value recommended by the assay’s manufacturer (>60 U/L). The highest agreement was obtained between the fPLI assay at the cut-off value of 3.5 μg/L and the DGGR-lipase assay at the cut-off value of 55 U/L (AC₁ = 0.725; CI 95%: 0.537, 0.914) and between the fPLI assay at the cut-off value of 5.3 μg/L and the DGGR-lipase assay at the cut-off value of 70 U/L (AC₁ = 0.749; CI 95%: 0.577, 0.921). The study confirms that the chance-corrected agreement between the two assays is good. Prospective studies comparing both assays to a diagnostic gold standard are needed to determine which of them is more accurate.