Molecular detection of Theileria equi and Babesia caballi in the bone marrow of asymptomatic horses

Expanding the universe of Piroplasmids: morphological detection and phylogenetic positioning of putative novel piroplasmids in black-eared opossums (Didelphis aurita) from southeastern Brazil, with description of "South American Marsupialia Group" of Piroplasmida

The growing proximity of wildlife to large urban niches arouses greater interest in understanding wild reservoirs in the epidemiology of diseases of importance to animal and human health. The aim of the present study was to investigate the presence of piroplasmids in opossums rescued from the metropolitan region of Rio de Janeiro state, Brazil. Blood and bone marrow samples were collected from 15 Didelphis aurita and subjected to DNA extraction and PCR using primers for the 18S rRNA, cox1, cox3, and hsp70 genes of piroplasmids. Clinical and hematological evaluation of the animals was also performed. Five (33.3%) of the 15 opossums tested positive for piroplasms in the nested PCR based on the 18S rRNA, and in two animals, it was possible to observe intra-erythrocytic structures compatible with merozoites. One of the positive animals showed clinical signs of infection such as jaundice, fever, and apathy. Anemia, low level of plasma protein, leukocytosis, and regenerative erythrocyte signs were observed in positive animals. Phylogenetic analysis based on both 18S rRNA and cox-3 genes demonstrated that the piroplasmids detected in D. aurita formed a unique sub-clade, albeit related to piroplasmids previously detected in Didelphis albiventris and associated ticks from Brazil. This study proposes the novel Piroplasmida Clade, namely "South American Marsupialia Group," and reinforces the need for new clinical-epidemiological surveys to understand the dynamics of these infections in didelphids in Brazil.

Eco-epidemiology of equine piroplasmosis and its associated tick vectors in Europe: A systematic literature review and a meta-analysis of prevalence

When studying a vector-borne disease, an eco-epidemiological approach is vital for a comprehensive understanding of how the pathogen circulates amongst populations. Equine piroplasmosis (EP), a tick-borne disease caused by the protozoans Babesia caballi and Theileria equi, is endemic in the Mediterranean basin of Europe and causes both animal health and economic issues for the equine sector. With no vaccine available, defining the episystem of the disease can help to identify which components of the host-pathogen-vector-environment system to target to improve preventive measures. In this systematic literature review, we collected relevant data on the eco-epidemiology of EP in Europe. The 62 studies remaining after the selection procedure explored potential vectors, indicators of parasite circulation and putative risk factors of EP. Eight hard tick species were identified as potential vectors of one or both piroplasm species. Meta-analyses were then conducted on prevalence and seroprevalence data in equids in European countries, demonstrating an estimated seroprevalence of 30% and 8% and prevalence of 25% and 2% for T. equi and B. caballi, respectively. Finally, herd management practices and environmental risk factors analysed in studies showed no real consensus between studies, but revealed a general trend highlighting age and exposure to ticks as risk factors, and vaccination as a protective factor. Through this study, we point out that only a few studies have focused on disease management practices and even fewer have studied the effect of environmental parameters on equid infections. Further investigation in these areas is required to better characterize the eco-epidemiology of EP and risk factors associated with this disease.

Biosafety Evaluation of Equine Umbilical Cord-Derived Mesenchymal Stromal Cells by Systematic Pathogen Screening in Peripheral Maternal Blood and Paired UC-MSCs

Background: The growing interest in mesenchymal stromal cells (MSCs) in equine medicine, together with the development of MSC biobanking for allogeneic use, raises concerns about biosafety of such products. MSCs derived from umbilical cord (UC) carry an inherent risk of contamination by environmental conditions and vertical transmission of pathogens from broodmares. There is yet no report in the scientific literature about horses being contaminated by infected MSC products, and no consensus about systematic infectious screening of umbilical cord-derived mesenchymal stromal cells (UC-MSCs) to ensure microbiological safety of therapeutic products. Objectives: To develop a standard protocol to ensure UC-MSC microbiological safety and to assess the risk of vertical transmission of common intracellular pathogens from broodmares to paired UC-MSCs. Study Design and Methods: Eighty-four UC and paired peripheral maternal blood (PMB) samples were collected between 2014 and 2016. Sterility was monitored by microbiological control tests. Maternal contamination was tested by systematical PMB PCR screening for 14 pathogens and a Coggins test. In case of a PCR-positive result regarding one or several pathogen(s) in PMB, a PCR analysis for the detected pathogen(s) was then conducted on the associated UC-MSCs. Results: Ten out of 84 UC samples were contaminated upon extraction and 6/84 remained positive in primo culture. The remaining 78/84 paired PMB & UC-MSC samples were evaluated for vertical transmission; 37/78 PMB samples were PCR positive for Equid herpesvirus (EHV)-1, EHV-2, EHV-5, Theileria equi, Babesia caballi, and/or Mycoplasma spp. Hepacivirus was detected in 2/27 cases and Theiler Diseases Associated Virus in 0/27 cases (not performed on all samples due to late addition). All paired UC-MSC samples tested for the specific pathogen(s) detected in PMB were negative (37/37). Main Limitations: More data are needed regarding MSC susceptibility to most pathogens detected in PMB. Conclusions: In-process microbiological controls combined with PMB PCR screening provide a comprehensive assessment of UC-MSC exposure to infectious risk, vertical transmission risk appearing inherently low.

Development and validation of a duplex real-time PCR assay for the diagnosis of equine piroplasmosis

Background

Equine piroplasmosis (EP) is an economically significant infection of horses and other equine species caused by the tick-borne protozoa Theileria equi and Babesia caballi. The long-term carrier state in infected animals makes importation of such subclinical cases a major risk factor for the introduction of EP into non-enzootic areas. Regulatory testing for EP relies on screening of equines by serological methods. The definitive diagnosis of EP infection in individual animals will benefit from the availability of sensitive direct detection methods, for example, when used as confirmatory assays for non-negative serological test results. The objectives of this study were to develop a real-time quantitative polymerase chain reaction (qPCR) assay for simultaneous detection of both agents of EP, perform comprehensive evaluation of its performance and assess the assay’s utility for regulatory testing.

Results

We developed a duplex qPCR targeting the ema-1 gene of T. equi and the 18S rRNA gene of B. caballi and demonstrated that the assay has high analytical sensitivities for both piroplasm species. Validation of the duplex qPCR on samples from 362 competitive enzyme-linked immunosorbent assay (cELISA)-negative horses from Canada and the United States yielded no false-positive reactions. The assay’s performance was further evaluated using samples collected from 430 horses of unknown EP status from a highly endemic area in Brazil. This set of samples was also tested by a single-target 18S rRNA qPCR for T. equi developed at the OIE reference laboratory for EP in Japan, and a previously published single-target 18S rRNA qPCR for B. caballi whose oligonucleotides we adopted for use in the duplex qPCR. Matching serum samples were tested for antibodies to these parasites using cELISA. By the duplex qPCR, T. equi-specific 18S rRNA qPCR and cELISA, infections with T. equi were detected in 87.9% (95% confidence interval, CI: 84.5–90.7%), 90.5% (95% CI: 87.3–92.3%) and 87.4% (95% CI: 84.0–90.2%) of the horses, respectively. The B. caballi prevalence estimates were 9.3% (95% CI: 6.9–12.4%) by the duplex qPCR and 7.9% (95% CI: 5.7–10.9%) by the respective single-target qPCR assay. These values were markedly lower compared to the seroprevalence of 58.6% (95% CI: 53.9–63.2%) obtained by B. caballi-specific cELISA. The relative diagnostic sensitivity of the duplex qPCR for T. equi was 95.5%, as 359 of the 376 horses with exposure to T. equi confirmed by cELISA had parasitemia levels above the detection limit of the molecular assay. In contrast, only 39 (15.5%) of the 252 horses with detectable B. caballi-specific antibodies were positive for this piroplasm species by the duplex qPCR.

Conclusions

The duplex qPCR described here performed comparably to the existing single-target qPCR assays for T. equi and B. caballi and will be more cost-effective in terms of results turnaround time and reagent costs when both pathogens are being targeted for disease control and epidemiological investigations. These validation data also support the reliability of the ema-1 gene-specific oligonucleotides developed in this study for confirmatory testing of non-negative serological test results for T. equi by qPCR. However, the B. caballi-specific qPCR cannot be similarly recommended as a confirmatory assay for routine regulatory testing due to the low level of agreement with serological test results demonstrated in this study. Further studies are needed to determine the transmission risk posed by PCR-negative equines with detectable antibodies to B. caballi.

Review of equine piroplasmosis

Equine piroplasmosis is caused by one of 2 erythrocytic parasites Babesia caballi or Theileria equi. Although the genus of the latter remains controversial, the most recent designation, Theileria, is utilized in this review. Shared pathogenesis includes tick-borne transmission and erythrolysis leading to anemia as the primary clinical outcome. Although both parasites are able to persist indefinitely in their equid hosts, thus far, only B. caballi transmits across tick generations. Pathogenesis further diverges after transmission to equids in that B. caballi immediately infects erythrocytes, whereas T.equi infects peripheral blood mononuclear cells. The recent re-emergence of T.equi in the United States has increased awareness of these tick-borne pathogens, especially in terms of diagnosis and control. This review focuses in part on factors leading to the re-emergence of infection and disease of these globally important pathogens.

Prevalence of Theileria equi, Babesia caballi, and Anaplasma phagocytophilum in horses from the north of Portugal

Piroplasmid protozoa Theileria equi and Babesia caballi and zoonotic rickettsial bacterium Anaplasma phagocytophilum are important agents of equine vector-borne diseases (EVBD). This study aimed at investigating the prevalence of infections with or exposure to these pathogens in horses from the north of Portugal. Blood was randomly collected from 162 horses, living in 72 different stables, to prepare Giemsa-stained slide smears. Additionally, plasma samples were tested for antibodies to T. equi and B. caballi by two competitive enzyme-linked immunosorbent assays and to A. phagocytophilum by an indirect fluorescence antibody test. Five horses were positive to T. equi by microscopy (3.1 %), three to B. caballi (1.9 %), and none to A. phagocytophilum with no horse simultaneously positive for the two piroplasms. Clinically suspect animals had a significantly higher positivity to T. equi by microscopy in comparison with the nonsuspect ones (21.4 vs. 1.4 %). Twenty-nine horses were seropositive to T. equi (17.9 %), 18 to B. caballi (11.1 %), and 21 to A. phagocytophilum (13.0 %). Combined serology and microscopy positive results to T. equi and B. caballi were 19.1 and 11.7 %, respectively, with 33.3 % of the horses found positive to at least one agent. Forty horses were positive to single agents and 14 to more than one agent. An outdoor or mixed outdoor/indoor type of housing was found to be a risk factor for the combined positivity to T. equi. Infections with T. equi, B. caballi, and A. phagocytophilum are endemic in the north of Portugal. In addition to the treatment of positive horses, preventive measures should be put in practice to reduce exposure to and infection with agents of EVBD.