Development of a SYBR Green Real-Time Polymerase Chain Reaction Assay for Quantitative Detection of Babesia Gibsoni (Asian Genotype) DNA

Standardization of quantitative PCR (qPCR) method to detect the level of parasitaemia in Babesia gibsoni infected dogs

The present investigation aimed to quantitatively assess the level of parasitemia in dogs using qPCR.The dogs selected for this study were infected with the haemoprotozoan parasite Babesia gibsoni. In the study, dogs diagnosed with babesiosis were divided into two groups (n = 12) and subjected to distinct treatment strategies. The first group received clindamycin-metronidazole-doxycycline (CMD) therapy, while the second group was treated with a combination of buparvaquone-azithromycin (BPV-AZM). The level of parasitemia in the infected dogs was determined using an absolute quantification-based qPCR method. This assessment was conducted both prior to initiating the treatment and on the 10th day following the commencement of the treatment protocols. On the tenth day after the initiation of treatment, the CMD group exhibited a lower level of parasitemia in comparison to the BPV-AZM group. In the CMD treated groups, the mean parasitemia decreased from 4.9E + 06 to 3.4E + 06, indicating a reduction in parasitic load. Conversely, in the BPV-AZM treatment groups, the mean parasitemia increased from 1.62E + 06 to 2.87E + 06, suggesting an increase in parasitic load. On the 10th day, the CMD-treated group demonstrated a statistically significant decline in the level of parasitemia, with a P-value of ≤0.001. This indicates a strong and significant reduction in parasitic load following the CMD treatment. Therefore, the absolute quantification-based qPCR method could effectively assess the initial treatment response by measuring the level of parasitemia.

A molecular and serological survey in Taiwan to determine the true risk of babesiosis in dogs not receiving regular tick prevention

Canine babesiosis is an important tick-borne disease worldwide. The prevalence varies between regions and countries; however, the incidence of tick infection is associated with the status of preventive tick control measures by the owner. To date, no studies have investigated the incidence of canine babesiosis and the condition of tick prevention in Taiwan. Therefore, the true risk of babesiosis could be underestimated in dogs that are not receiving tick prophylaxis. Samples were collected at 51 hospitals around Taiwan from 265 dogs not receiving regular tick prophylaxis. Diagnostic real-time PCR was performed, and 28 dogs (10.6%) were positive for Babesia spp., including B. gibsoni (26/28) and B. vogeli (2/28). Thirty-nine dogs (14.7%) were seropositive to B. gibsoni. Take the real-time PCR positive as the Babesia infected case, the positive and negative predictive value of serological assay were 64.1% and 98.7%, respectively. The seropositivity of B. gibsoni was significantly associated with real-time PCR positivity for Babesia spp. and vice versa (p < 0.001). The odds of seropositive representing real-time PCR positivity was 132.7 times greater than the seronegative (OR: 132.731, 95% CI 35.683-493.728). Risk factors in the population identified included: dogs with a short-haired coat; intact dogs; dogs from multi-dog households; dogs with more than 10 ticks and fleas on the skin; dogs that go outdoors more than 9 times per week; and dogs with an abnormal blood test result that included anemia, thrombocytopenia, and leukopenia. However, the dogs were not tested for other co-infections, therefore, these hematological risk factors should be carefully interpreted and confirmed by further diagnostic tests. In conclusion, when dogs present with abnormal blood test results and share the risk factors listed above, babesiosis should be seriously considered and followed up with molecular and serological testing. The serological assay used in this study can provide valuable information in diagnosing babesiosis in dogs in Taiwan.

Rapid identification of Babesia canis and Babesia gibsoni (Asian genotype) in canine blood samples using a customized portable real-time PCR analyzer and TaqMan-based assay

Canine babesiosis is a serious infectious disease in subtropical and tropical regions. Typically, clinical detection of canine babesiosis is performed by blood smear observation or the traditional polymerase chain reaction (PCR). Herein, we developed a new TaqMan-based real-time PCR assay combined with a customized portable real-time PCR platform for a rapid and accurate detection of canine babesiosis. Two new primer/probe pairs (B18S and BITS1) were designed based on 18S ribosomal RNA and an internal transcribed spacer 1 (ITS1) sequence to differentiate Babesia canis and B. gibsoni (Asian genotype) DNAs from canine blood samples. Additionally, a corresponding customized compact real-time PCR platform with low 6-carboxyfluorescein fluorescence detection (≤5 nM), including a fast and accurate thermal cycling ability with a user-friendly interface for thermal control and data analysis, was designed for the limited space use. Both assays (B18S and BITS1) demonstrated a sensitivity of 100 copies/reaction based on the 95 % confidence interval evaluation method. The self-developed customized portable real-time PCR analyzer presented high repeatability and reproducibility with the TaqMan-based assay. Moreover, 501 clinical specimens were collected for evaluating the performance of the proposed PCR. The positive and negative predictive values were 90 % (18 of 20) and 100 % (226 of 226), respectively, for samples suspected with B. canis infection and 98 % (55 of 56) and 100 % (199 of 199), respectively, for samples suspected with B. gibsoni infection.

A novel PCR-based point-of-care method enables rapid, sensitive and reliable diagnosis of Babesia gibsoni infection in dogs

BACKGROUND

Babesia gibsoni (B. gibsoni) is an intraerythrocytic protozoan parasite of dogs that causes fever and hemolytic illness. A timely diagnosis is essential for the disease management.

RESULTS

Here, we report a QubeMDx PCR system which enables a rapid, sensitive and reliable diagnosis of B. gibsoni near the dog patient. Within 30 min, this diagnostic assay was able to detect as low as 0.002% parasitemia of the dog blood. Using clinical samples, this new assay was validated to demonstrate 100% agreement with real-time PCR.

CONCLUSIONS

This novel diagnostic method provides a reliable point-of-care test to assist in the identification of B. gibsoni.

Mitochondrial cytochrome oxidase C subunit III (cox3) gene as a sensitive and specific target for molecular detection of Babesia gibsoni infection in dogs

A PCR targeting mitochondrial cytochrome oxidase subunit III (cox3) for molecular detection of Babesia gibsoni infection in dogs has been developed in this study. Fifty blood samples from suspected clinical cases from dogs, brought to the veterinary college clinics, were examined for presence of B. gibsoni using conventional diagnosis by microscopic examination of Giemsa stained thin blood smears. In addition, species specific PCRs targeting ITS-1 region (BgITS-1 PCR) and nested PCR targeting 18S ribosomal RNA gene (Bg18SnPCR) were carried out. A 634 bp PCR fragment of B. gibsoni cox3 gene was amplified in positive samples from three geographical locations of Satara, Wai and Pune in Maharashtra state of India. From analysis of the sequence of the B. gibsoni cox3 gene, we found that the Indian isolate had 96-98% similarity to the isolate from Japan and China. Post sequencing, de-novo diagnostic primer pair for species specific amplification of 164 bp fragment of B. gibsonicox3 was designed and the PCR was standardized. The diagnostic results of de-novo Bgcox3 PCR were compared with BgITS-1 PCR and Bg18S nPCR. Thin blood smears detected 22% (11/50) samples positive for small form of Babesia species. The BgITS-1 PCR detected 25% samples (15/50) as positive and Bg18S nPCR detected 80% (40/50) B. gibsoni positive samples. The de-novo Bgcox3 PCR detected 66% (33/50) samples positive for B. gibsoni (at 95% CI). The analytical sensitivity of cox3 PCR was evaluated as 0.000003% parasitaemia or 09 parasites in 100  μl of blood. The de-novo diagnostic cox3 PCR did not cross react with control positive DNA from other haemoprotozoa and rickettsia like B. vogeli, Hepatozoon canis, Trypanosoma evansi, Ehrlichia canis and Anaplasma platys. Statistically, cox3 PCR had better diagnostic efficiency than ITS-1 PCR in terms of sensitivity (p = 0.0006). No statistically significant difference between results of cox3 PCR and 18S nPCR was observed (p = 0.1760). Kappa values estimated for each test pair showed fair to moderate agreement between the observations. Specificity of Bgcox3 PCR was 100% when compared with microscopy or BgITS-1 PCR. Sensitivity of Bgcox3 PCR was 100% when compared with that of Bg18S nPCR.

Detection of Babesia gibsoni in dogs by combining recombinase polymerase amplification (RPA) with lateral flow (LF) dipstick

Babesia gibsoni is a protozoan parasite responsible for the majority of reported cases of canine babesiosis in China. Currently, microscopic examination of the Giemsa-stained thin blood smears is the main diagnosis method in clinic. Here, we report the recombinase polymerase amplification-lateral flow (LF-RPA) dipstick detection method for targeting B. gibsoni cytochrome c oxidase subunit I (cox I) gene. The reaction takes only 20-30 min under isothermal temperatures between 30 and 45 °C. Specificity was evaluated using DNA from related apicomplexan parasites and their host, while the sensitivity was calculated based on the DNA from the experimental B. gibsoni-infected dogs. Results indicated that the LF-RPA method is 20 times more sensitive than the conventional PCR based on 18S rRNA and has no cross reaction with any other test DNAs. The applicability of the LF-RPA method was further evaluated using 15 samples collected from clinic. Thirteen of the 15 samples (86.67%) were detected as positive by LF-RPA, while 10 of them (66.67%) were found positive by conventional PCR. Overall, the novel LF-RPA assay is effective for the detection of B. gobsini and has considerable advantages over the conventional PCR in sensitivity, specificity, simplicity in operation, less time consumption, and visual detection. The LF-RPA method may facilitate the surveillance and early detection of B. gibsoni infection in dogs.

Molecular detection of Hepatozoon canis in dogs from Kerala

India has a wide range of agro-climatic zones which is highly conducive for a diverse range of vectors and canines are continuously exposed to the risk of spectrum of tick borne protozoan diseases. The brown dog tick, Rhipicephalus sanguineus is widely prevalent among dogs in Kerala and there is a high prevalence of this tick transmitted Babesia and Ehrlichia spp. infection. However, the incidence of Hepatozoon canis transmitted by the same tick species had not been reported in the state since 2004. Preliminary screening of client owned dogs revealed six dogs to be positive for typical gelatin capsule shaped gamonts of H. canis within neutrophils in blood smear by microscopic examination. A PCR assay was standardized to amplify a specific 737 bp fragment of 18S rRNA gene of H. canis. Phylogenetic analysis revealed closest relationship with West Indies isolate deposited at GenBank database. The present study records the molecular detection of this haemoparasite in the state, for the first time.

Detection of Ehrlichia, Anaplasma, and Babesia spp. in dogs of Cebu, Philippines

Background

Ehrlichia, Anaplasma, and Babesia spp. are canine pathogens transmitted by the Rhipicephalus sanguineus tick which can cause varied clinical signs. These pathogens have been investigated in the Philippines, but coinfection has not been reported yet.

Aim

The aim of this study was to evaluate the presence of Ehrlichia/Anaplasma and Babesia spp. in Philippine dogs.

Materials and Methods

A total of 100 dogs from seven different veterinary establishments in Cebu, Philippines, were examined for Ehrlichia/Anaplasma and Babesia spp. infection using peripheral blood smear examination and polymerase chain reaction (PCR). Inclusion criteria included a history or presence of tick infestation, anemia, and/or thrombocytopenia. Clinical signs were recorded. Statistical analyses were performed between PCR positivity and clinical signs and hematological results.

Results

A total of 10 and 18 dogs were found to be positive for Ehrlichia/Anaplasma and Babesia spp., respectively. One animal was PCR positive for both pathogens, which is the first report of coinfection in the country. The most common clinical signs observed include inappetence (89%), lethargy (80%), thrombocytopenia (85%), and anemia (74%). Analyses revealed that inappetence (p=0.044) and weight loss (p=0.028) were found statistically significant with Ehrlichia/Anaplasma infection. Basophil (p=0.001) and eosinophil counts (p=0.000) were also found significantly different between Ehrlichia/Anaplasma spp.-positive and -negative dogs. On the other hand, differential monocyte count (p=0.009) was found significantly different between Babesia spp.-positive and -negative dogs.

Conclusion

The present study showed low infection rates of canine ehrlichiosis/anaplasmosis and babesiosis and provided additional evidence for the presence of the pathogens in the area.

Improved molecular detection of Babesia infections in animals using a novel quantitative real-time PCR diagnostic assay targeting mitochondrial DNA

BACKGROUND

Babesiosis is a protozoal, tick transmitted disease found worldwide in humans, wildlife and domesticated animals. Commonly used approaches to diagnose babesiosis include microscopic examination of peripheral blood smears, detection of circulating antibodies and PCR. To screen and differentiate canine Babesia infections many PCR assays amplify the 18S rRNA gene. These sequences contain hypervariable regions flanked by highly conserved regions allowing for amplification of a broad-range of Babesia spp. However, differences in the 18S rRNA gene sequence of distantly related clades can make it difficult to design assays that will amplify all Babesia species while excluding the amplification of other eukaryotes. By targeting Babesia mitochondrial genome (mtDNA), we designed a novel three primer qPCR with greater sensitivity and broader screening capabilities to diagnose and differentiate Babesia spp.

METHODS

Using 13 Babesia mtDNA sequences, a region spanning two large subunit rRNA gene fragments (lsu5-lsu4) was aligned to design three primers for use in a qPCR assay (LSU qPCR) capable of amplifying a wide range of Babesia spp. Plasmid clones were generated and used as standards to determine efficiency, linear dynamic range and analytical sensitivity. Animals naturally infected with vector-borne pathogens were tested retrospectively and prospectively to determine relative clinical sensitivity and specificity by comparing the LSU qPCR to an established 18S rDNA qPCR.

RESULTS

The LSU qPCR efficiencies ranged between 92 and 100% with the limit of detection at five copies/reaction. The assay did not amplify mammalian host or other vector-borne pathogen gDNA except Cytauxzoon felis (a feline protozoal pathogen). The LSU qPCR assay amplified 12 different Babesia. sp. and C. felis from 31/31 (100%) archived samples, whereas the 18S qPCR amplified only 26/31 (83.9%). By prospective analysis, 19/394 diagnostic accessions (4.8%) were LSU qPCR positive, compared to 11/394 (2.8%) 18S rDNA qPCR positive.

CONCLUSIONS

We have developed a more sensitive qPCR assay with a more expansive range of Babesia spp. detection by targeting a highly conserved region of mtDNA, when compared to an established 18S qPCR.

Trematode Fluke Procerovum varium as Cause of Ocular Inflammation in Children, South India

Larvae of this fluke are novel causes of granulomatous eye disease in children.

Trematodes are recognized as a group of emerging parasites in tropical countries. We identified a trematode as a cause of ocular granulomas that developed in children who bathed in ponds or rivers in South India. DNA was isolated from patients’ surgically excised granulomas and from the trematode cercariae (larvae) released by the snail Melanoidestuberculata in water in which the children bathed. Real-time and conventional PCRs were performed that targeted ribosomal DNA regions spanning the internal transcribed spacer 2 and 28S sequences of this trematode. The PCR-amplified products were subjected to bidirectional sequencing. Analysis of sequences for the granuloma samples and the trematode cercariae showed maximum sequence similarity with Procerovumvarium (family Heterophyidae). Our results confirmed the etiology of the ocular infection, implicating snail vectors as environmental risk factors for ocular parasitosis.

New Molecules in Babesia gibsoni and their application for diagnosis, vaccine development, and drug discovery

Babesia gibsoni is an intraerythrocytic apicomplexan parasite that causes piroplasmosis in dogs. B. gibsoni infection is characterized clinically by fever, regenerative anemia, splenomegaly, and sometimes death. Since no vaccine is available, rapid and accurate diagnosis and prompt treatment of infected animals are required to control this disease. Over the past decade, several candidate molecules have been identified using biomolecular techniques in the authors' laboratory for the development of a serodiagnostic method, vaccine, and drug for B. gibsoni. This review article describes newly identified candidate molecules and their applications for diagnosis, vaccine production, and drug development of B. gibsoni.

Canine babesiosis in northwestern India: molecular detection and assessment of risk factors

In the current study, a total of 214 blood samples from dogs in and around Ludhiana, Punjab (India), suspected for canine babesiosis were examined with conventional and molecular assays. Examination of Giemsa-stained peripheral thin blood smears revealed an overall prevalence of 7.47% (16/214) for canine babesiosis encompassing 0.93% (2/214) of large Babesia and 6.54% (14/214) of Babesia gibsoni. However, molecular diagnosis revealed 15.42% (33/214) samples positive for B. gibsoni infection as evident by the presence of 671 bp amplicon. The results of multivariate analysis showed that the prevalence of B. gibsoni was associated with various risk factors, namely, age (P < 0.001; OR: 0.398; CI 95%: 0.080–1.799), sex (P = 0.022; OR: 0.849; CI 95%: 0.403–1.791), breed of host (P = 0.371; OR: 3.345; CI 95%: 1.045–10.710), and season (P = 0.230; OR: 2.143; CI 95%: 0.788–5.830). The prevalence of B. gibsoni was higher in summer as compared to winter season and in younger dogs, while breed and sex of the host were not significantly associated with the occurrence of the disease.

Babesia infection in naturally exposed pet dogs from a north-eastern state (Assam) of India: detection by microscopy and polymerase chain reaction

The objective of the study was to detect Babesia infections in pet dogs of a north-eastern state of India. The diagnostic efficacy of Babesia infection by polymerase chain reaction (PCR) technique has been compared with microscopy examination. For this, a total of 111 blood samples of pet dogs presented at clinical complex of the College of Veterinary Science, Guwahati, Assam with clinical signs suspected for Babesia infection subjected to the study. A total of 44 (39.63 %) dogs were diagnosed as positive for Babesia infections after microscopic examination. Among these, Babesia canis infection was diagnosed in 5 dogs (4.50 %) and B. gibsoni infection in 39 (35.13 %) dogs microscopically in Giemsa stained blood smears. Molecular diagnosis using PCR detected 63 (56.75 %) dogs positive for Babesia infection. Single infection with B. canis was found in 9 (8.10 %) dogs while B. gibsoni alone was detected in 3 (2.70 %) dogs. Mixed infections by both these species were detected in 51 (45.94 %) dogs. Overall, PCR detected 54 (48.64 %) dogs as B. gibsoni and 60 (54.05 %) dogs as B. canis positive.

Current advances in detection and treatment of babesiosis

Babesiosis is a disease with a world-wide distribution affecting many species of mammals principally cattle and man. The major impact occurs in the cattle industry where bovine babesiosis has had a huge economic effect due to loss of meat and beef production of infected animals and death. Nowadays to those costs there must be added the high cost of tick control, disease detection, prevention and treatment. In almost a century and a quarter since the first report of the disease, the truth is: there is no a safe and efficient vaccine available, there are limited chemotherapeutic choices and few low-cost, reliable and fast detection methods. Detection and treatment of babesiosis are important tools to control babesiosis. Microscopy detection methods are still the cheapest and fastest methods used to identify Babesia parasites although their sensitivity and specificity are limited. Newer immunological methods are being developed and they offer faster, more sensitive and more specific options to conventional methods, although the direct immunological diagnoses of parasite antigens in host tissues are still missing. Detection methods based on nucleic acid identification and their amplification are the most sensitive and reliable techniques available today; importantly, most of those methodologies were developed before the genomics and bioinformatics era, which leaves ample room for optimization. For years, babesiosis treatment has been based on the use of very few drugs like imidocarb or diminazene aceturate. Recently, several pharmacological compounds were developed and evaluated, offering new options to control the disease. With the complete sequence of the Babesia bovis genome and the B. bigemina genome project in progress, the post-genomic era brings a new light on the development of diagnosis methods and new chemotherapy targets. In this review, we will present the current advances in detection and treatment of babesiosis in cattle and other animals, with additional reference to several apicomplexan parasites.

Molecular diagnosis of infections and resistance in veterinary and human parasites

Since 1977, >2000 research papers described attempts to detect, identify and/or quantify parasites, or disease organisms carried by ecto-parasites, using DNA-based tests and 148 reviews of the topic were published. Despite this, only a few DNA-based tests for parasitic diseases are routinely available, and most of these are optional tests used occasionally in disease diagnosis. Malaria, trypanosomiasis, toxoplasmosis, leishmaniasis and cryptosporidiosis diagnosis may be assisted by DNA-based testing in some countries, but there are very few cases where the detection of veterinary parasites is assisted by DNA-based tests. The diagnoses of some bacterial (e.g. lyme disease) and viral diseases (e.g. tick borne encephalitis) which are transmitted by ecto-parasites more commonly use DNA-based tests, and research developing tests for these species makes up almost 20% of the literature. Other important uses of DNA-based tests are for epidemiological and risk assessment, quality control for food and water, forensic diagnosis and in parasite biology research. Some DNA-based tests for water-borne parasites, including Cryptosporidium and Giardia, are used in routine checks of water treatment, but forensic and food-testing applications have not been adopted in routine practice. Biological research, including epidemiological research, makes the widest use of DNA-based diagnostics, delivering enhanced understanding of parasites and guidelines for managing parasitic diseases. Despite the limited uptake of DNA-based tests to date, there is little doubt that they offer great potential to not only detect, identify and quantify parasites, but also to provide further information important for the implementation of parasite control strategies. For example, variant sequences within species of parasites and other organisms can be differentiated by tests in a manner similar to genetic testing in medicine or livestock breeding. If an association between DNA sequence and phenotype has been demonstrated, then qualities such as drug resistance, strain divergence, virulence, and origin of isolates could be inferred by DNA-based tests. No such tests are in clinical or commercial use in parasitology and few tests are available for other organisms. Why have DNA-based tests not had a bigger impact in veterinary and human medicine? To explore this question, technological, biological, economic and sociological factors must be considered. Additionally, a realistic expectation of research progress is needed. DNA-based tests could enhance parasite management in many ways, but patience, persistence and dedication will be needed to achieve this goal.

Sequence and phylogenetic analysis of the thrombospondin-related adhesive protein (TRAP) gene of Babesia gibsoni isolates from dogs in Taiwan

The genetic diversity of Babesia gibsoni strains worldwide is currently poorly defined. The aim of the present study was to characterize B. gibsoni strains in naturally infected dogs in Taiwan using a combination of polymerase chain reaction (PCR) and sequence analysis of both 18S rDNA and the gene encoding thrombospondin-related adhesive protein (TRAP). Genomic DNA was extracted from 29 parasitemic dogs, and the target genes were separately amplified, sequenced and aligned with corresponding sequences available in GenBank. All 18S rDNA sequences (1,262 bp) amplified from the Taiwanese isolates were identical to each other and had very high similarity (99.9-100%) with previously reported B. gibsoni sequences. These results provide the first molecular evidence showing infection of dogs with B. gibsoni from Taiwan. On the other hand, a phylogenetic analysis based on the deduced amino acid sequence of the TRAP gene demonstrated that the Taiwanese isolates were closely related to strains previously identified from Okinawa Island, Japan, but genetically distinct from strains found on Honshu in Japan and Jeju Island in South Korea. The divergence of TRAP among the geographically dispersed strains examined in this study and others supports the conclusion that this gene is useful for molecular genotyping of B. gibsoni strains.

Application of the SYBR Green real-time HRM PCR technique in the differentiation of the Babesia canis canis protozoa isolated in the areas of eastern Poland

The aim of this study was to determine the usefulness of the real-time polymerised chain reaction (PCR) high-resolution melting (HRM) method in the differentiation of the Babesia canis canis protozoa isolated from dogs in the areas of eastern Poland. The studies involved 20 isolates of B. canis canis qualified depending on the analysis of the 18S RNA gene sequence to group A (EU 622792) and 20 isolates qualified to group B (EU 622793). It was proven with the real-time PCR technique that the melting temperature (Tm) of the obtained products of amplification was 78 degrees C for the representatives of group A and 81 degrees C for the representatives of group B, which proves that the real-time SYBR Green HRM PCR method is a technique allowing for the differentiation of the B. canis isolates which are slightly different with respect to the genetic structure, without the necessity to carry out time-consuming studies, i.e., sequencing and restriction fragment length polymorphism.

Canine babesiosis: from molecular taxonomy to control

Canine babesiosis is a clinically significant emerging vector-borne disease caused by protozoan haemoparasites. This review article considers recent literature pertaining to the taxonomic classification of Babesia and Theileria species affecting dogs and the geographical distribution of these parasites. The diagnosis of canine babesiosis by traditional, molecular and serological methods is reviewed, together with recent advances in our understanding of the pathophysiology of piroplasmosis, and of the treatment and prevention of this disease.

Evaluation of efficacy of bruceine A, a natural quassinoid compound extracted from a medicinal plant, Brucea javanica, for canine babesiosis

Bruceine A, a natural quassinoid compound extracted from the dried fruits of Brucea javanica (L.) Merr., was evaluated for its antibabesial activity in vitro and in vivo. Bruceine A inhibited the in vitro growth of Babesia gibsoni in canine erythrocytes at lower concentration compared with the standard antibabesial drug diminazene aceturate and killed the parasites within 24 hr at a concentration of 25 nM. Oral administration of bruceine A at a dosage of 6.4 mg/kg/day for 5 days resulted in no clinical findings in a dog with normal ranges of hematological and biochemical values in the blood. Three dogs were infected with B. gibsoni and two of them were treated with bruceine A at a dosage of 6.4 mg/kg/day for 6 days from day 5 post-infection. An untreated dog developed typical acute babesiosis symptoms including severe anemia, high fever, and complete loss of appetite and movement. However, the two bruceine A-treated dogs maintained their healthy conditions throughout the experimental period of 4 weeks although complete elimination of parasites from the peripheral blood was not achieved and decreases in the packed cell volume and the erythrocyte and platelet counts were observed. Since natural quassinoid compounds have been used as traditional medicines for the treatment of various ailments including cancer and malaria, the present results suggest that bruceine A or other related compounds are potential candidates for the treatment of canine babesiosis.

A quantitative PCR assay for the detection and quantification of Babesia bovis and B. bigemina

The haemoparasites Babesia bovis and Babesia bigemina affect cattle over vast areas of the tropics and temperate parts of the world. Microscopic examination of blood smears allows the detection of clinical cases of babesiosis, but this procedure lacks sensitivity when parasitaemia levels are low. In addition, differentiating between similar haemoparasites can be very difficult. Molecular diagnostic procedures can, however, overcome these problems. This paper reports a quantitative PCR (qPCR) assay involving the use of SYBR Green. Based on the amplification of a small fragment of the cytochrome b gene, this method shows both high sensitivity and specificity, and allows quantification of parasite DNA. In tests, reproducible quantitative results were obtained over the range of 0.1 ng to 0.1 fg of parasite DNA. Melting curve analysis differentiated between B. bovis and B. bigemina. To assess the performance of the new qPCR procedure it was used to screen for babesiosis in 40 cows and 80 horses. B. bigemina was detected in five cows (three of these were also found to be positive by standard PCR techniques targeting the 18S rRNA gene). In addition, B. bovis was detected in one horse and B. bigemina in two horses using the proposed method, while none was found positive by ribosomal standard PCR. The sequences of the B. bigemina cytochrome b and 18S rRNA genes were completely conserved in isolates from Spain and Argentina, while those of B. bovis showed moderate polymorphism.

PCR-RFLP for the detection and differentiation of the canine piroplasm species and its use with filter paper-based technologies

Canine piroplasmosis is an emerging disease worldwide, with multiple species of piroplasm now recognised to infect dogs. A nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was developed for the detection and differentiation of each of the piroplasm species currently known to infect dogs on the basis of the 18S ribosomal RNA gene. The assay can potentially amplify and discriminate between Theileria annae, Theileria equi, Babesia conradae, Babesia gibsoni, Babesia sp. (Coco) and each of the Babesia canis subspecies. Non-canine piroplasm species can also potentially be detected using the described assay, however amplification of Neospora caninum was also observed. The PCR was found to have a high detection limit, capable of detecting a 2.7x10(-7)% parasitaemia or the equivalent of 1.2 molecules of target DNA when using DNA extracted from whole EDTA blood and detected a parasitaemia of 2.7x10(-5)% using blood applied to both Flinders Technology Associates (FTA) cards and IsoCodetrade mark Stix. The application of blood samples to filter paper may greatly assist in piroplasm identification in regions of the world where local technologies for molecular characterisation are limited. The assay reported here has the potential to be standardised for routine screening of dogs for piroplasmosis.

Sensitive measure of prevalence and parasitaemia of haemosporidia from European blackbird (Turdus merula) populations: value of PCR-RFLP and quantitative PCR

Haemosporidian parasites are common in birds in which they act as an important selective pressure. While most studies so far have focused on the effect of their prevalence on host life-history traits, no study has measured the effect of parasitaemia. We developed molecular methods to detect, identify and quantify haemosporidia in 2 natural populations of the Blackbird Turdus merula. Three different parasite genotypes were found - 1 Haemoproteus and 2 Plasmodium. A PCR-RFLP screening revealed that only approximately 3% of blackbirds were free of parasites, compared to the 34% of uninfected birds estimated by blood smear screening. A quantitative PCR (q-PCR) assay revealed a weaker parasitaemia in microscopically undetected parasites compared to microscopically detected ones. Large parasitaemia differences were found between parasite species, suggesting either differing parasite life-histories or host resistance. Parasitaemias were also weaker in male hosts, and in urban habitats, suggesting that both host factors (e.g. immunity) and habitat characteristics (e.g. vector availability) may modulate parasite density. Interestingly, these differences in parasitaemia were comparable to differences in parasite prevalence estimated by smear screening. This suggests that previous results obtained by smear screening should be reinterpreted in terms of parasitaemia instead of parasite prevalence.