Parasites on paper—The use of FTA Elute® for the detection of Dirofilaria repens microfilariae in canine blood

Dried Blood Spots technology for veterinary applications and biological investigations: technical aspects, retrospective analysis, ongoing status and future perspectives

Dried Blood Spots (DBS) technology has become a valuable tool in medical studies, however, in veterinary and biological research DBS technology applications are still limited. Up-to-date no review has comprehensively integrated all the evidence existing across the fields, technologies and animal species. In this paper we summarize the current applications of DBS technology in the mentioned areas, and provide a scope of different types of dried sample carriers (cellulose and non-cellulose), sampling devices, applicable methods for analyte extraction and detection. Mammals, birds, insects and other species are represented as the study objects. Besides the blood, the review considers a variety of specimens, such as milk, saliva, tissue samples and others. The main applications of dried samples highlighted in the review include epidemiological surveys and monitoring for infections agents or specific antibodies for disease/vaccination control in households and wildlife. Besides the genetic investigations, the paper describes detection of environmental contaminants, pregnancy diagnosis and many other useful applications of animal dried samples. The paper also analyses dried sample stability and storage conditions for antibodies, viruses and other substances. Finally, recent developments and future research for DBS technology in veterinary medicine and biological sciences are discussed.

Detection of Antibodies Against Toxoplasma gondii in Filter Paper-Dried Blood Dot Spots Compared with Serum in Pigs and Assessment of Variation Associated with Packed Cell Volume

The aim of this study was to assess the agreement between anti-Toxoplasma gondii IgG antibody detection in serum and filter paper (FP) blood spots using the indirect immunofluorescence antibody assay (IFA) and to evaluate the potential impact of the packed cell volume (PCV) on antibody detection in FPs. A pair of a serum and an FP sample was collected from 96 sows at various farms in Greece, with previously identified high seropositivity and/or risk factors associated with high seropositivity against T. gondii. The PCV value was determined using the microhematocrit method. IFA was used for the detection of antibodies against T. gondii. T. gondii-specific antibodies were detected in 45.8% serum samples and 41.6% FP samples showing almost perfect agreement. Detection in FP samples presented high sensitivity (87.1-92.8%) and excellent specificity (100%) when compared with detection in serum, regardless of the PCV values. The findings of this study support the reliability of FPs for the evaluation of the serological status of swine against T. gondii. FPs could be a good alternative sample type compared with serum for large-scale epidemiological studies.

Membrane Technology for Rapid Point-of-Care Diagnostics for Parasitic Neglected Tropical Diseases

Parasitic neglected tropical diseases (NTDs) affect over one billion people worldwide, with individuals from communities in low-socioeconomic areas being most at risk and suffering the most. Disease management programs are hindered by the lack of infrastructure and resources for clinical sample collection, storage, and transport and a dearth of sensitive diagnostic methods that are inexpensive as well as accurate. Many diagnostic tests and tools have been developed for the parasitic NTDs, but the collection and storage of clinical samples for molecular and immunological diagnosis can be expensive due to storage, transport, and reagent costs, making these procedures untenable in most areas of endemicity. The application of membrane technology, which involves the use of specific membranes for either sample collection and storage or diagnostic procedures, can streamline this process, allowing for long-term sample storage at room temperature. Membrane technology can be used in serology-based diagnostic assays and for nucleic acid purification prior to molecular analysis. This facilitates the development of relatively simple and rapid procedures, although some of these methods, mainly due to costs, lack accessibility in low-socioeconomic regions of endemicity. New immunological procedures and nucleic acid storage, purification, and diagnostics protocols that are simple, rapid, accurate, and cost-effective must be developed as countries progress control efforts toward the elimination of the parasitic NTDs.

Rapid Detection and Typing of Actinobacillus pleuropneumoniae Serovars Directly From Clinical Samples: Combining FTA® Card Technology With Multiplex PCR

Actinobacillus pleuropneumoniae (APP), the causative agent of porcine pleuropneumonia, is highly contagious and responsible for high morbidity, mortality, and economic losses in the swine industry worldwide, but quick serotyping and diagnosis are still not widely available. In this study, we sought to validate the use of Whatman FTA® cards for collection and processing of A. pleuropneumoniae isolates, or porcine lung tissue samples, for direct use in diagnostic multiplex PCRs. We have optimized the processing of 3-mm discs punched from FTA® cards loaded with cultured A. pleuropneumoniae, or imprinted on lesioned regions of lung tissue, with only three distilled water washes before addition into our APP-multiplex PCR (mPCR) assay for rapid, low-cost identification and serotyping. DNA captured on FTA® cards generated the same diagnostic PCR results as DNA extracted using commercial kits for 85 A. pleuropneumoniae clinical isolate cultures and 22 lung samples. Additionally, bacterial DNA bound to FTA® cards was detectable by PCR after 6 months of storage at 37°C. This study provides simple, efficient, rapid, and practical sample processing for detection and molecular serotyping of A. pleuropneumoniae.

Long-Term Preservation and Storage of Faecal Samples in Whatman® Cards for PCR Detection and Genotyping of Giardia duodenalis and Cryptosporidium hominis

Preservation and conservation of biological specimens, including faecal samples, is a challenge in remote areas or poor-resource settings where the cold chain cannot be maintained. This study aims at evaluating the suitability of filter cards for long-term storage of faecal samples of animal and human origin positive to the diarrhoea-causing protozoan parasites, Giardia duodenalis and Cryptosporidium hominis. Three commercially available Whatman^® Filter Cards were comparatively assessed: the FTA^® Classic Card, the FTA^® Elute Micro Card, and the 903 Protein Saver Card. Human faecal samples positive to G. duodenalis (n = 5) and C. hominis (n = 5) were used to impregnate the selected cards at given storage (1 month, 3 months, and 6 months) periods and temperature (-20 °C, 4 °C, and room temperature) conditions. Parasite DNA was detected by PCR-based methods. Sensitivity assays and quality control procedures to assess suitability for genotyping purposes were conducted. Overall, all three Whatman^® cards were proven useful for the detection and molecular characterisation of G. duodenalis and C. hominis under the evaluated conditions. Whatman^® cards represent a simple, safe, and cost-effective option for the transportation, preservation, and storage of faecal samples without the need of the cold chain.

Canine vector-borne pathogens in semi-domesticated dogs residing in northern Cambodia

Background

In Southeast Asia, the canine vector-borne pathogens Babesia spp., Ehrlichia canis, Anaplasma platys, Hepatozoon canis, haemotropic mycoplasmas and Dirofilaria immitis cause significant morbidity and mortality in dogs. Moreover, dogs have also been implicated as natural reservoirs for Rickettsia felis, the agent of flea-borne spotted fever, increasingly implicated as a cause of undifferentiated fever in humans in Southeast Asia. The objective of this study was to determine the prevalence and diversity of canine vector-borne pathogens in 101 semi-domesticated dogs from rural Cambodia using molecular diagnostic techniques.

Results

The most common canine vector-borne pathogens found infecting dogs in this study were Babesia vogeli (32.7 %) followed by Ehrlichia canis (21.8 %), Dirofilaria immitis (15.8 %), Hepatozoon canis (10.9 %), Mycoplasma haemocanis (9.9 %) and “Candidatus Mycoplasma haematoparvum” (2.9 %). A high level of co-infection with CVBD agents (23.8 %) was present, most commonly B. vogeli and E. canis. Naturally occurring R. felis infection was also detected in 10.9 % of dogs in support of their role as a natural mammalian reservoir for flea-borne spotted fever in humans.

Conclusions

This study reports for the first time, the prevalence and diversity of CVBD pathogens in dogs in Cambodia. In total, five species of CVBD pathogens were found infecting semi-domesticated dogs and many were co-infected with two or more pathogens. This study supports the role of dogs as natural mammalian reservoirs for R. felis, the agent of flea-borne spotted fever in humans.

Morphological and molecular detection of canine dirofilarial species of veterinary and medical importance in Morogoro municipality, Tanzania

A descriptive cross-sectional survey of Dirofilaria infections in dogs was carried out from January to March 2015 in Morogoro municipality, Tanzania. One hundred and fifty two blood samples were collected from healthy dogs aged more than 6 months living in different areas of Morogoro, and analyzed by modified Knott's technique for circulating microfilariae. Microfilaraemic samples were further analyzed by Polymerase chain reaction (PCR) and PCR products were sequenced for molecular identification. Microfilariae were detected by microscopy in 9 samples (5.92%), of which 6 tested positive by PCR. The 5.8S-internal transcribed spacer 2 (ITS2)-28S ribosomal DNA (rDNA) sequences generated were 97% identical to Dirofilaria immitis and 86% to 90% identical to D. repens, confirming the presence of D. immitis in Tanzania and showing the presence of D. repens, not previously observed.

Evaluation of FTA ® paper for storage of oral meta-genomic DNA

AIM

The purpose of the present study was to evaluate the short-term storage of meta-genomic DNA from native oral biofilms on FTA(®) paper.

MATERIALS AND METHODS

Thirteen volunteers of both sexes received an acrylic splint for intraoral biofilm formation over a period of 48 hours. The biofilms were collected, resuspended in phosphate-buffered saline, and either stored on FTA(®) paper or directly processed by standard laboratory DNA extraction. The nucleic acid extraction efficiencies were evaluated by 16S rDNA targeted SSCP fingerprinting. The acquired banding pattern of FTA-derived meta-genomic DNA was compared to a standard DNA preparation protocol. Sensitivity and positive predictive values were calculated.

RESULTS

The volunteers showed inter-individual differences in their bacterial species composition. A total of 200 bands were found for both methods and 85% of the banding patterns were equal, representing a sensitivity of 0.941 and a false-negative predictive value of 0.059.

CONCLUSION

Meta-genomic DNA sampling, extraction, and adhesion using FTA(®) paper is a reliable method for storage of microbial DNA for a short period of time.

A survey of canine filarial diseases of veterinary and public health significance in India

BACKGROUND

Dirofilaria spp., Acanthocheilonema spp. and Brugia spp. have all been reported in Indian dogs. In previous studies, diagnosis was made by morphological identification only. This is the first geographically stratified cross-sectional study in India to determine the prevalence and geographical distribution of canine filarial species of veterinary and public health importance, using a combination of conventional and molecular diagnostic techniques.

RESULTS

A total of 139 from 525 dogs (26.5%; 95% CI 22.7, 30.3) were positive for microfilariae. The most common species of canine filaria identified in this study was A. reconditum (9.3%) followed by D. repens (6.7%) and D. immitis (1.5%). Three out of 525 dogs were found to have mixed infections on PCR. The morphological and molecular evidence on the sequence of the 18S gene and phylogenetic analysis of the ITS-2 region provided strong evidence that the canine microfilariae discovered in the Himalayan city of Ladakh belong to a novel species of Acanthocheilonema. Two dogs in Ladakh were also found to have mixed infections of the novel species described above and a unique microfilaria which morphologically resembled Microfilaria auquieri Foley, 1921.

CONCLUSIONS

At least six species of filarial nematode are now known to infect dogs in India, two of which were reported for the first time in this study. The study also confirms and extends the geographical distribution of canine heartworm (D. immitis) which overlaps with D. repens, emphasising the importance for veterinary clinicians and diagnostic laboratories to utilise immunodiagnostic tests that will not cross-react between those two filarial species. From a public health viewpoint, the distribution and prevalences of these nematodes warrant an appropriate prophylaxis to be administered to dogs.