The development and evaluation of a loop-mediated isothermal amplification (LAMP) method for detection of Babesia spp. infective to sheep and goats in China

Anaemia in Sheep Caused by Babesia and Theileria Haemoparasites

Piroplasmoses in sheep are caused by vector-borne apicomplexan protozoa, Babesia and Theileria. Different species are responsible for the disease; some species are more pathogenic than others and have a worldwide distribution. In this sense, these causative agents can cause anaemia in flocks. In general, these vector-borne diseases infect small ruminants and cause host-mediated pathology. In the case of Babesia species, a combination of different mechanisms is involved: red blood cell lysis due to intracellular parasite multiplication, activation of biogenic amines and the coagulation system with the possibility of disseminated intravascular coagulation. By contrast, less information is available on the different immunopathogenic mechanisms involved in the development of anaemia in sheep with theileriosis. However, the mechanisms of pathogenic action in theileriosis are similar to those studied in babesiosis. Diagnosis is based on compatible clinical signs, laboratory findings, specific diagnostic tests and the presence of the tick vector. Some of these tests detect the causative agent itself, such as direct identification by light microscopy and molecular analysis. In contrast, other tests detect the sheep's immune response to the organism by serology. Both diseases pose a significant diagnostic challenge for veterinary practitioners around the world. This review presents the most frequent clinical signs, pathogenesis and clinicopathological findings, diagnosis.

A universal ELISA assay for detecting six strains of ovine Babesia species in China

Ovine babesiosis, caused by genus of Babesia, is a zoonotic disease and mainly transmitted by hard ticks. It has led to enormous economic losses to the sheep industry in China. In the present study, an ELISA assay for simultaneous detection six strains of Babesia spp., including B. motasi Lintan, B. motasi Tianzhu, B. motasi Hebei, B. motasi Ningxian, Babesia sp. Xinjiang and Babesia sp. Dunhuang, was developed using Apical Membrane Antigen 1 (AMA1) as candidate diagnostic antigen. The sensitivity and specificity of the established ELISA were 97.4 % and 98.0 %, respectively. Relatively high level of specific antibodies could be detected from 12th day to 126th day after sheep experimentally infected with Babesia spp.. A small scale of field sera was investigated using the developed ELISA assay, and the average positive rate was 51.98 %. This study provides an easy to operate, cost effective and time saving approach, which is suitable for both field and experimental samples, thus it could be a useful tool in epidemiological investigations and diagnoses of ovine babesiosis.

Stable transfection system for Babesia sp. Xinjiang

BACKGROUND

Stable transfection systems have been described in many protozoan parasites, including Plasmodium falciparum, Cryptosporidium parvum, Babesia bovis, Babesia ovata, and Babesia gibsoni. For Babesia sp. Xinjiang (Bxj), which is the causative pathogen of ovine babesiosis and mainly prevails across China, the platform of those techniques remains absent. Genetic manipulation techniques are powerful tools to enhance our knowledge on parasite biology, which may provide potential drug targets and diagnostic markers.

METHODS

We evaluated the inhibition efficiency of blasticidin (BSD) and WR99210 to Bxj. Then, a plasmid was constructed bearing selectable marker BSD, green fluorescent protein (GFP) gene, and rhoptry-associated protein-1 3' terminator region (rap 3' TR). The plasmid was integrated into the elongation factor-1 alpha (ef-1α) site of Bxj genome by cross-over homologous recombination technique. Twenty μg of plasmid was transfected into Bxj merozoites. Subsequently, drug selection was performed 24 h after transfection to generate transfected parasites.

RESULTS

Transfected parasite lines, Bxj-c1, Bxj-c2, and Bxj-c3, were successfully obtained after transfection, drug selection, and colonization. Exogenous genes were integrated into the Bxj genome, which were confirmed by PCR amplification and sequencing. In addition, results of western blot (WB) and indirect immunofluorescence assay (IFA) revealed that GFP-BSD had expressed for 11 months.

CONCLUSIONS

In our present study, stable transfection system for Bxj was successfully developed. We anticipate that this platform will greatly facilitate basic research of Bxj.

Optimization of a Loop-Mediated Isothermal Amplification Assay as a Point-of-Care Tool for the Detection of Wuchereria bancrofti in Human Blood in Tana River Delta, Kenya

INTRODUCTION

Accurate detection of filarial parasites in humans and vectors is essential for the implementation and evaluation of Global and National Programs to eliminate lymphatic filariasis. Immunological methods to detect infection are available; however, cross-reactivity issues have been reported in most of them. Nucleic acid-based molecular assays offer high levels of specificity and sensitivity and can be used to detect the infections.

METHODS

In this study, we evaluated loop-mediated isothermal amplification (LAMP) tests to amplify Wuchereria bancrofti DNA in patients' blood. The amplicons were tested by both pH-sensitive dyes for enhanced visual detection and agarose gel electrophoresis. A closed-tube LAMP assay was also evaluated. Cohen's Kappa statistics was used for statistical analysis of the assays. 125 patients consented for blood sampling which were used for clinical analysis of LAMP assays with the PCR method used as the "gold standard."

RESULTS

The sensitivity of the evaluated Wuchereria bancrofti LAMP was 92.3%, with a specificity of 97.3% and kappa statistics value of 0.84, which is in a strong agreement.

CONCLUSION

In this study, LAMP assays coupled with fluorescence dye detection have been found to be suitable for diagnosis and monitoring of Wuchereria bancrofti infections in the Kenyan population.

Challenges in Tick-Borne Pathogen Detection: The Case for Babesia spp. Identification in the Tick Vector

The causative agents of Babesiosis are intraerythrocytic protozoa of the genus Babesia. Babesia parasites are present around the world, affecting several mammals including humans, pets and livestock, hence its medical and veterinary relevance. Babesia spp. detection in its invertebrate host is a main point in understanding the biology of the parasite to acquire more knowledge on the host–Babesia–vector interactions, as increasing knowledge of the Babesia lifecycle and babesiosis epidemiology can help prevent babesiosis outbreaks in susceptible mammals. The aim of the present review is to highlight the newest findings in this field, based on a bibliographic compilation of research studies recently carried out for the detection of the main Babesia species found in tick vectors affecting mammalian hosts, including the different tick stages such as adult ticks, larvae, nymphs and eggs, as well as the detection method implemented: microscopic tools for parasite identification and molecular tools for parasite DNA detection by conventional PCR, nested-PCR, PCR-RFLP, PCR-RLB hybridization, real time-PCR, LAMP and RAP assays. Although molecular identification of Babesia parasites has been achieved in several tick species and tissue samples, it is still necessary to carry out transmission experiments through biological models to confirm the vectorial capacity of various tick species.

Rapid detection of Babesia motasi responsible for human babesiosis by cross-priming amplification combined with a vertical flow

Background

Babesia motasi is known as an etiological agent of human and ovine babesiosis. Diagnosis of babesiosis is traditionally performed by microscopy, examining Giemsa-stained thin peripheral blood smears. Rapid detection and accurate identification of species are desirable for clinical care and epidemiological studies.

Methods

An easy to operate molecular method, which requires less capital equipment and incorporates cross-priming amplification combined with a vertical flow (CPA-VF) visualization strip for rapid detection and identification of B. motasi.

Results

The CPA-VF targets the 18S rRNA gene and has a detection limit of 50 fg per reaction; no cross reaction was observed with other piroplasms infective to sheep or Babesia infective to humans. CPA-VF and real-time (RT)-PCR had sensitivities of 95.2% (95% confidence interval, CI 78.1–99.4%) and 90.5% (95% CI 72–97.6%) and specificities of 95.8 (95% CI 80.5–99.5%) and 97.9 (95% CI 83.5–99.9%), respectively, versus microscopy and nested (n) PCR combined with gene sequencing. The clinical performance of the CPA-VF assay was evaluated with field blood samples from sheep (n = 340) in Jintai county, Gansu Province, and clinical specimens (n = 492) obtained from patients bitten by ticks.

Conclusions

Our results indicate that the CPA-VF is a rapid, accurate, nearly instrument-free molecular diagnostic approach for identification of B. motasi. Therefore, it could be an alternative technique for epidemiological investigations and diagnoses of ovine and/or human babesiosis caused by B. motasi, especially in resource-limited regions.

First molecular evidence of Babesia occultans and Theileria separata infection in ticks and sheep in China

Protozoan parasites of the genus Babesia and Theileria are significant tick-borne pathogens of domestic animals and cause economic losses to the livestock industry in tropical and subtropical regions worldwide. In this study, 274 blood samples and 32 tick samples were collected from four counties of Wuwei City in northwestern China in June and July in 2018. The DNA from the field samples was analyzed for Babesia or Theileria infection using specific PCR and sequencing based on 18S rRNA gene fragments. The total infection rates were 0.4% for B. motasi and T. separata (both 1/274) in sheep, 3.1% for T. annulata (1/32), 6.2% for B. occultans (2/32) and 9.4% for B. bigemina (3/32) in ticks, respectively. In particular, T. separata has been for the first time detected in sheep in China and B. occultans in Hyalomma asiaticum from Gansu Province of China.

Rapid diagnosis of Theileria annulata by recombinase polymerase amplification combined with a lateral flow strip (LF-RPA) in epidemic regions

Rapid and accurate diagnosis of Theileria annulata infection contributes to the formulation of strategies to eradicate this parasite. A simple and efficient diagnostic tool, recombinase polymerase amplification (RPA) combined with a lateral flow (LF) strip, was used in detection of Theileria and compared to other methods that require expensive instruments and skilled personnel. Herein, we established and optimized an LF-RPA method to detect the cytochrome b gene of T. annulata mitochondrial DNA from experimentally infected and field-collected blood samples. This method has many unparalleled characteristics, including that it is rapid (clear detection in 5min at constant temperature), sensitive (the limitation of detection is at least 2pg genomic DNA), and specific (no cross-reaction with other piroplasms that infect cattle). The LF-RPA assay was evaluated via testing 17 field blood samples and comparing the results of that of a PCR, showing 100% agreement, which demonstrates the ability of the LF-RPA assay to detect T. annulata infections in small number of samples (n=17). Taken together, the results indicate that this method could be used as an ideal diagnostic tool for detecting T. annulata in endemic regions with limited to fewer and local resources and could also be a potential technique for the surveillance and control of blood protozoa.

Genetic characterization and molecular survey of Babesia sp. Xinjiang infection in small ruminants and ixodid ticks in China

Babesia sp. Xinjiang is a large ovine Babesia species that was recently isolated in China. Compared with other ovine Babesia species, it has different morphological features, pathogenicity and vector tick species. The known transmitting vector is Hyalomma anatolicum. In this study, the distribution and the presence of Babesia sp. Xinjiang in small ruminants and ixodid ticks in China were assessed by specific nested-PCR assay based on the rap-1a gene. A total of 978 blood samples from sheep or goats from 15 provinces and 797 tick specimens from vegetation from 10 provinces were collected and analysed for the presence of the Babesia sp. Xinjiang. Full-length and partial rap-1a of Babesia sp. Xinjiang were amplified from field samples. The PCR results were further confirmed by DNA sequencing. Overall, 38 (3.89%) blood samples and 51 (6.4%) tick samples were positive for Babesia sp. Xinjiang infection. The highest presence (26.92%) was found in blood samples from Yunnan province, while H. qinghaiensis ticks with the highest presence of infection (21.3%) were from Gansu province. This study identified for the first time Babesia sp. Xinjiang infection in H. longicornis tick species. The rap-1a sequences of Babesia sp. Xinjiang from field blood and tick samples indicated 100% identity. The presence of Babesia sp. Xinjiang infection may increase in China. Novel potential transmitting vectors might be more extensive than previously thought.

Development and Evaluation of a Loop-Mediated Isothermal Amplification (Lamp) Assay for the Detection of Haemonchus contortus in Goat Fecal Samples

Haemonchus contortus is one of the most significant strongylid nematodes infecting small ruminants, and it causes great economic losses to the livestock industry worldwide. Accurate diagnosis of H. contortus is crucial to control strategies. Traditional microscopic examinations are the most common methods for the diagnosis of H. contortus , but they are time-consuming and inaccurate. Molecular methods based on PCR are more accurate, but need expensive machines usually only used in the laboratory. Loop-mediated isothermal amplification (LAMP) is a rapid, simple, specific, and sensitive method that has been widely used to detect viruses, bacteria, and parasites. In the present study, a LAMP method targeting ribosomal ITS-2 gene for detection of the H. contortus in goat fecal samples has been established. The established LAMP method was H. contortus specific, and the sensitivity of LAMP was the same as that of the H. contortus species-specific PCR, with the lowest DNA level detected as being 1 pg. Examination of the clinical samples indicated that the positive rate of LAMP was higher than that of PCR, but no statistical difference was observed between LAMP and PCR (χ² = 17.991, P = 0.053). In conclusion, a LAMP assay with a high specificity and a good sensitivity has been developed to detect H. contortus infection in goats. The established LAMP assay is useful for clinical diagnosis of H. contortus .

Genetic diversity and molecular characterization of Babesia motasi-like in small ruminants and ixodid ticks from China

Ovine babesioses, an important tick-borne disease of sheep and goats in China, is caused by the reproduction of intraerythrocytic protozoa of the Babesia genus. Babesia motasi-like is a Babesia parasite that infects small ruminant in China, and two sub-groups of B. motasi-like can be subdivided based on differences in the rhoptry-associated-protein-1 gene. This study aimed to characterize the distribution, epidemiology and genetics of B. motasi-like in animals and ticks. A molecular investigation was carried out from 2009 to 2015 in 16 provinces in China. In total, 1081 blood samples were collected from sheep and goats originating from 27 different regions, and 778 ixodid tick samples were collected from 8 regions; the samples were tested for the presence of B. motasi-like using a specific nested PCR assay based on the rap-1b gene. The results indicated that 139 (12.9%), 91 (8.4%), 48 (4.4%) and 6 (0.7%) of the blood samples were positive for general B. motasi-like, Babesia sp. BQ1 (Lintan and Ningxian), Babesia sp. Tianzhu and Babesia sp. Hebei sub-groups, mixed infections, respectively. Among the collected 778 ixodid ticks (including Haemaphysalis longicornis, Haemaphysalis qinghaiensis, Dermacentor silvarum, Ixodes persulcatus, Rhipicephalus sanguineus and Rhipicephalus (Boophilus) microplus), the most frequently infected with Babesia were D. silvarum and I. persulcatus (35.7%), followed by H. longicornis (26.8%), H. qinghaiensis (24.8%) and R. sanguineus (9.3%). The PCR results were confirmed by DNA sequencing. The positive rates of B. motasi-like infection in ticks were found to be higher in China, compared with previous studies in other countries. B. motasi-like infections have not previously been reported in D. silvarum, I. persulcatus or R. sanguineus. The findings obtained in this study could be used for planning effective control strategies against babesiosis in China.

Molecular detection of Babesia ovis in sheep and ticks using the gene encoding B. ovis surface protein D (BoSPD)

The gene encoding Babesia ovis surface protein D (BoSPD) was cloned from B. ovis cDNA library. This gene encodes a polypeptide chain of 155 amino acids, including a predicted 22 amino acid signal peptide. Sequence analysis of the BoSPD suggested that it is a surface protein with no known domains. BLAST analysis followed by multiple alignments showed four orthologs from other Apicomplexan species and suggested that BoSPD is specific for B. ovis. BoSPD-based PCR was then developed to specifically detect B. ovis in experimentally-infected sheep and Rhipicephalus bursa ticks, as well as in field samples. The PCR enabled detection of B. ovis at a calculated parasitemia of 0.0016% and was shown to be specific for B. ovis. Moreover, the BoSPD PCR allowed detection of prolonged subclinical infection in experimentally-infected lambs and in dissected organs of experimentally-infected ticks. Finally, the PCR was used to detect parasitemia in blood samples from naturally-infected sheep and in R. bursa ticks collected from sheep in an infected flock. These results suggest that the BoSPD gene sequence can be used as a specific and sensitive marker, allowing detection of subclinical parasitemia in sheep and in ticks. Based on its predicted properties, BoSPD may be considered as a candidate for anti-B. ovis vaccine development or a target for anti-B.ovis treatment.

Transmission of Babesia ovis by different Rhipicephalus bursa developmental stages and infected blood injection

In this report, the transmission efficacy of Babesia ovis, the principal causative agent of ovine babesiosis, was studied by infestation of lambs with different Rhipicephalus bursa stages or by injection of infected blood. Infected blood injection induced acute babesiosis in splenectomized lambs, while only mild clinical signs were observed in intact animals. Both splenectomized and intact lambs developed high antibody titer, detectable for at least 180 days post infection. Infestation of splenectomized and intact lambs with infected tick larvae did not induce clinical babesiosis or specific serum response in any of the examined animals. Similarly, infestation of one splenectomized lamb with partially-fed infected R. bursa males did not induce any clinical response or seroconversion. Nymph infestation caused a mild clinical response followed by specific seroconversion, in one out of five lambs. All animals infested with infected unfed adults (males and females) showed mild-to-severe clinical signs 8 to 12 days post infestation. The acute phase was followed by a marked seroconversion. Our results indicate that the principal transmission of B. ovis is performed by adult R. bursa ticks, and that the host reaction can last as long as 6 months following the acute infection.

Discrimination between ovine Babesia and Theileria species in China based on the ribosomal protein S8 (RPS8) gene

Ovine babesiosis and theileriosis are important hemoprotozoal diseases of sheep and goats in tropical and subtropical regions that lead to economic losses in these animals. PCR-restriction fragment length polymorphism (PCR-RFLP) is a reliable molecular diagnostic tool for discriminating Theileria or Babesia species in the same host. In this study, the DNA sequences of a ribosomal protein S8 (RPS8) gene from four species of piroplasms in China were used to develop a species-specific PCR-RFLP diagnostic tool. The sensitivity of the PCR assays was 0.1 pg DNA for B. motasi and 1 pg DNA for T. uilenbergi and 10 pg DNA for Babesia sp. Xinjiang-2005 and T. luwenshuni. The clear size difference of the PCR products allowed for a direct discrimination for B. motasi, Babesia sp. Xinjiang-2005 and ovine Theileria species (T. uilenbergi and T. luwenshuni), except that the mixed infection between T. uilenbergi and T. luwenshuni may be difficult to distinguish, simply after the electrophoretic separation of the amplification products. Further T. uilenbergi and T. luwenshuni diagnoses were made by digesting the PCR product with SacI. The established method could be applicable for the survey of parasite dynamics, and epidemiological studies as well as prevention and control of the disease.

A sero-epidemiological survey of Chinese Babesia motasi for small ruminants in China

Babesia motasi BQ1 (Lintan) was first isolated from Haemaphysalis qinghaiensis collected in Gannan Tibet Autonomous Region, Gansu province in April 2000. In this study, a total of 3,204 serum samples from small ruminants in 22 provinces located in different districts of China were tested for antibodies against merozoite antigens from cultured B. motasi BQ1 (Lintan) by enzyme-linked immunosorbent assay. This method can survey the prevalence of low-pathogenic Chinese B. motasi. The results of this survey indicated that the average positive rate was 43.5 %, and the positive rates of investigated provinces were significantly different from 6.1 to 91.0 %, and the infections had been found in all provinces investigated. Our data provide large important information regarding the current sero-prevalence of B. motasi in China.

Rapid identification and differentiation of Theileria sergenti and Theileria sinensis using a loop-mediated isothermal amplification (LAMP) assay

The present study developed and validated a species-specific loop-mediated isothermal amplification (LAMP) assay for the rapid detection and discrimination of two benign bovine Theileria species -T. sergenti and T. sinensis. The LAMP assay is inexpensive and easy to perform and involves a rapid reaction-the amplification can be performed in 55 min or 50 min under isothermal conditions of 61°C or 63°C, respectively, by employing a set of four species-specific primer mixtures. The results can be checked using agarose gels. The optimal assay conditions, under which the assay exhibited with no cross-reaction with other closely related tick-borne parasites (T. annulata, Babesia bovis, B. bigemina, B. major, B. ovata, B. U. sp., Anaplasma marginale) or between the two Theileria species of interest, was established. The assay is approximately 10-fold more sensitive than the conventional specific PCR assay. The LAMP assay was validated using DNA from 6 standard stocks in the laboratory and was evaluated for its diagnostic utility using blood samples collected from experimentally and naturally infection cattle or yaks in China. These findings indicate that this Theileria species-specific LAMP assay may have potential clinical applications for the detection and differentiation of two benign bovine Theileria species -T. sergenti and T. sinensis, especially in endemic countries.

Babesia ovis as the main causative agent of sheep babesiosis in Iran

Babesiosis is a haemoparasitic disease with high economical losses in livestock industry worldwide. The early diagnosis and successful therapy of babesiosis belong to the key steps of control and health management of livestock. Ethanol-fixed blood samples of 400 sheep were analyzed for Babesia infection. Reverse line blot (RLB) was established specifically for Theileria lestoquardi, Theileria (China 1), Theileria (China 2), Theileria ovis, Theileria separata, Babesia ovis, Babesia motasi, Babesia crassa, and Babesia (Lintan). The DNA was extracted from the ethanol-fixed blood samples and amplified with a common primer pair derived from 18S rRNA gene, amplifying both Theileria spp. as well as Babesia spp. Regarding the differences in the length of nucleotide sequences of the polymerase chain reaction (PCR) products obtained from Theileria spp. and Babesia spp., the PCR products derived from Babesia spp. were out screened and analyzed by RLB. The RLB analysis showed that 28 samples within the 400 blood samples were B. ovis positive. No B. motasi, B. crassa, or Babesia (Lintan) could be detected. The sequence analysis of one PCR product as a representative for other B. ovis-positive PCR products confirmed the results of RLB. Our results and the results of other investigators showed that B. ovis could be considered as a main causative agent of sheep babesiosis in Iran. Furthermore, our results also showed that RLB can be used as a reliable method for a simultaneous differentiation of Theileria and Babesia species from each other.

A recently identified ovine Babesia in China: serology and sero-epidemiology

Babesia sp. in Xinjiang, transmitted by Hyalomma, is a large Babesia that is infective for small ruminants, but it has almost no pathogenicity in healthy sheep. On the basis of the sequences of the 18S rRNA and internal transcribed spacer (ITS) genes, morphological characteristics, vector tick species and pathogenicity it was identified recently as a novel Babesia species. In the present study, an enzyme-linked immunosorbent assay (ELISA) was developed using soluble merozoite antigens of Babesia sp. in Xinjiang (BXJMA) derived from in vitro culture. When the positive threshold was chosen as 24.65% of the specific mean antibody rate, the specificity and sensitivity were both 97.3%. There was no cross-reaction between BXJMA and positive sera from sheep infected with other Chinese ovine piroplasms or Anaplasma ovis in the ELISA and western blotting. Specific antibodies against Babesia sp. in Xinjiang could be detected 2 weeks post infection and a high level of antibodies persisted for more than 12 weeks in experimentally infected sheep. The ELISA was tested on 3857 sera collected from small ruminants in 50 prefectures of 22 provinces to evaluate the sero-epidemiology of Babesia sp. in Xinjiang infection, and the average positive rate was 31.66%. These data provide that the developed ELISA is a powerful tool for the sero-diagnosis of Babesia sp. in Xinjiang and confirm that it is a novel species.

Advances in diagnosis of protozoan diseases

Microscopy still remains the gold standard procedure for the diagnosis of many protozoan infections in animals, but the specific identification requires skilled and experienced personnel. Immunoassays, detecting antibodies or specific protozoan antigens, have been developed but often lack sensitivity and specificity due to close relationship between many protozoa. Recent research has focussed almost exclusively on molecular based techniques for the identification and quantification of parasite DNA in samples. Opinion differ on most appropriate targets to use and there are very few diagnostic kits available making comparison between laboratories difficult. Future research needs to focus on robust, cheap field diagnostic assays.

Loop-mediated isothermal amplification (LAMP) assays for the detection of Theileria annulata infection in China targeting the 18S rRNA and ITS sequences

We have developed two loop-mediated isothermal amplification (LAMP) assays for the detection of Theileria annulata, an economically important cattle disease in China that occurs in subtropical and tropical areas. These assays target the ribosomal RNA (18S rRNA) and ITS LAMP sequences. The primer set for each gene target consists of four primers, and each set recognizes six distinct regions on the target gene to allow for the highly specific detection of T. annulata. The specific ladder bands were amplified from the autologous genomic DNA of four Chinese-laboratory-preserved standard T. annulata stocks, and there were no cross-reactions with the genomic DNA of normal bovine blood and other protozoan species. The LAMP assays were sufficiently sensitive to detect 0.1 pg/μl of genomic DNA. Furthermore, DNA extracted from blood collected from cattle experimentally infected with T. annulata (18-105 days post-infection) was amplified, demonstrating the high sensitivity of these primers. Of the 351 field samples collected from China, 24.5% were positively detected by two LAMP primers, and 18.2% were found to be positive for T. annulata infection by PCR. These results indicate that the LAMP assay could be a potential diagnostic tool for epidemiological studies of T. annulata infection in China.

Simultaneous detection of piroplasma infections in field Haemaphysalis qinghaiensis ticks by reverse line blotting

Piroplasmosis is caused by tick-borne haemoprotozoan parasites in the genera of Theileria and Babesia, in which numbers of agents are highly pathogenic for cattle, sheep and goats. We developed a reverse line blot (RLB) assay for detection and differentiation of four different parasites, in which 18S ribosomal RNA gene sequence was amplified with a set of universal primers specific for all members in the genera of Theileria and Babesia; and the probes were designed on the basis of hypervariable region 4 (V4 region) of 18S rRNA gene. Three Theileria and one Babesia can be detected simultaneously on this system and it was sensitive to detect a parasitemia level between 10(-5) and 10(-8)%. A total of 149 Haemaphysalis qinghaiensis ticks collected from Lintan County of Gannan Tibetan Autonomous Region was tested by RLB. Among these, 136 tick samples were also tested by a nested PCR assay developed previously. After comparison of these results, it showed that more T. luwenshuni was detected in RLB assay, while more T. uilenbergi was detected in H. qinghaiensis ticks by nested PCR. The RLB has shown capability for simultaneous detection of four species of piroplasm in H. qinghaiensis ticks, indicating its usefulness for epidemiological studies of piroplasmosis.

BQP35 is a novel member of the intrinsically unstructured protein (IUP) family which is a potential antigen for the sero-diagnosis of Babesia sp. BQ1 (Lintan) infection

A new gene of Babesia sp. BQ1 (Lintan) (BQP35) was cloned by screening a merozoite cDNA expression library with infected sheep serum and using rapid amplification of cDNA ends (RACE). The nucleotide sequence of the cDNA was 1140bp with an open reading frame (ORF) of 936bp encoding a 35-kDa predicted polypeptide with 311 amino acid residues. Comparison of BQP35 cDNA and genomic DNA sequences showed that BQP35 does not possess an intron. Recombinant BQP35 (rBQP35), expressed in a prokaryotic expression system, showed abnormally slow migration on SDS-PAGE. Gel shifting, amino acid sequence and in silico disorder region prediction indicated that BQP35 protein has characteristics of intrinsically unstructured proteins (IUPs). This is the first description of such proteins in the Babesia genus. BQP35 induced antibodies production as early as one week after Babesia sp. BQ1 (Lintan) infection in sheep. No cross-reaction was observed with sera from sheep infected with other ovine piroplasms dominant in China, except with Babesia sp. Tianzhu. The interest of BQP35 as a diagnostic antigen is discussed.

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 test for vivax malaria with loop-mediated isothermal amplification method in central China

Vivax malaria has the highest incidence in central China. High-throughput and cost-effective testing methods are essential for vivax malaria diagnosis in this area. Loop-mediated isothermal amplification (LAMP) is an established nucleic acid amplification method, which provides a promising platform for the molecular detection of malaria parasites in development countries. This study was performed to compare the LAMP method, the nested PCR-based method, and microscopic examinations in diagnosing vivax malaria. LAMP detected vivax malaria parasites in 160 of 164 microscopically positive samples (sensitivity, 97.6%), whereas nested PCR detected Plasmodium vivax in 162 of 164 samples (sensitivity, 98.8%). No false-positive results were obtained by LAMP or nested PCR among fever-positive and healthy samples. The sensitivities and specificities of the two molecular tests were consistently high. In addition, the reproducibility of the LAMP assays using water bath, which reduced the cost substantially. LAMP method is an accurate, rapid, simple, and cost-effective method that may be useful for diagnosis in field diagnoses instead of nested PCR. This method is feasible to diagnose vivax malaria parasite in endemic areas of central China.

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.

Comparative diagnosis of malaria infections by microscopy, nested PCR, and LAMP in northern Thailand

Three methods, microscopy, nested polymerase chain reaction (nPCR), and loop-mediated isothermal amplification (LAMP) have been applied for malaria diagnosis in 105 human blood samples collected in Northern Thailand. Only Plasmodium falciparum and Plasmodium vivax infections were detected. A total number of 57 positives (54%) could be detected for P. falciparum and 25 (24%) for P. vivax when all samples that were positive in any of the three methods are counted together. The nPCR was used as a reference standard for comparison with the other methods, microscopy and LAMP. The sensitivity of LAMP for P. falciparum was 100%. All nPCR-negative samples for P. falciparum were also negative by both microscopy and LAMP (specificity, 100%). For diagnosis of P. vivax, microscopy detected 15 of 23 nPCR-positive samples (sensitivity, 65%). LAMP detected 22 of 23 nPCR-positives (sensitivity, 96%). Among the 82 nPCR-negative samples microscopy detected two samples (specificity, 98%). All 82 nPCR-negative were also negative by the LAMP method (specificity, 100%). Both Plasmodium genus- and species-specific LAMP primer sets yielded the same results in all samples. There were no significant differences in the prevalence detected by each method. We assume that LAMP was as reliable as nPCR and more reliable than microscopy in the detection of Plasmodium DNA tested in the examined Thai field blood samples. This study further validates LAMP as an alternative molecular diagnostic tool, which can be used in the diagnosis of early infections of malaria cases and together with nPCR can also be used as supplementary methods for clinical and epidemiological use.

Course of infection by Babesia sp. BQ1 (Lintan) and B. divergens in sheep depends on the production of IFNgamma and IL10

Ovine babesiosis is an important disease in China and responsible for economic losses. Several Babesia strains are involved, but Babesia sp. BQ1 (Lintan) and Babesia sp. BQ1 (Ningxian) are particularly prevalent in the Guansu region. Babesia divergens, in contrast, can experimentally infect spleen-intact sheep, but does not induce clinical signs. The immune response of spleen-intact sheep to Babesia sp. BQ1 (Lintan) and to B. divergens was therefore compared to identify the immune mechanisms involved in pathogenicity. The greater pathogenicity of Babesia sp. BQ1 (Lintan) than that of B. divergens was confirmed: sheep infected with Babesia sp. BQ1 (Lintan), but not with B. divergens, developed hyperthermia and showed patent parasitaemia in Giemsa-stained blood smears from the ear vein. Furthermore, more parasites were also detected in the blood from the jugular vein of Babesia sp. BQ1 (Lintan)-infected sheep. Pathogenicity of Babesia spp. involved cellular responses, but not humoral responses. Interferon-gamma was produced only by specifically activated PBMC from B. divergens-infected sheep and interleukin-10 only by specifically activated PBMC from Babesia sp. BQ1 (Lintan)-infected sheep. The role of these cytokines in the course of infection by Babesia spp. is discussed.

Merozoite proteins from Babesia sp. BQ1 (Lintan) as potential antigens for serodiagnosis by ELISA

Babesia sp. BQ1 (Lintan) is a Babesia isolated from sheep infested with Haemaphysalis qinghaiensis in China, and is closely related to B. motasi based on the 18S rRNA gene sequence. In the present study, an ELISA was developed with merozoite antigens of Babesia sp. BQ1 (Lintan) (BQMA) purified from in vitro culture. When the positive threshold was chosen as 30% of the antibodies rate, evaluated with 198 negative sera, the specificity was 95.5%. Except for Babesia sp. Tianzhu, there was no cross-reaction between BQMA and positive sera from Babesia sp. BQ1 (Ningxian)-, Babesia sp. Hebei-, Babesia sp. Xinjiang-, Theileria luwenshuni-, T. uilenbergi-, or Anaplasma ovis-infected sheep, which are the dominant haemoparasites of small ruminants in China. Specific antibodies against Babesia sp. BQ1 (Lintan) were produced 1 or 2 weeks post-infection and a high level of antibodies persisted for more than 8 months in experimentally infected sheep. This ELISA was tested on 974 sera collected from field-grazing sheep in 3 counties of Gansu province, northwestern China to evaluate the seroprevalence of Babesia sp. BQ1 (Lintan) infection and the average positive rate was 66.84%. The feasibility of increasing the specificity of this BQMA-based ELISA, by using some BQMA antigens for serodiagnosis is discussed.

Diagnosis of parasitic diseases: old and new approaches

Methods for the diagnosis of infectious diseases have stagnated in the last 20–30 years. Few major advances in clinical diagnostic testing have been made since the introduction of PCR, although new technologies are being investigated. Many tests that form the backbone of the “modern” microbiology laboratory are based on very old and labour-intensive technologies such as microscopy for malaria. Pressing needs include more rapid tests without sacrificing sensitivity, value-added tests, and point-of-care tests for both high- and low-resource settings. In recent years, research has been focused on alternative methods to improve the diagnosis of parasitic diseases. These include immunoassays, molecular-based approaches, and proteomics using mass spectrometry platforms technology. This review summarizes the progress in new approaches in parasite diagnosis and discusses some of the merits and disadvantages of these tests.

Sensitive and rapid detection of Schistosoma japonicum DNA by loop-mediated isothermal amplification (LAMP)

In this study, a loop-mediated isothermal amplification (LAMP) assay was established to detect Schistosoma japonicum DNA in faecal and serum samples of rabbits, and serum samples of humans infected with S. japonicum. This LAMP assay was based on the sequence of highly repetitive retrotransposon SjR2, and was able to detect 0.08 fg S. japonicum DNA, which is 10(4) times more sensitive than conventional PCR. The LAMP assay was also highly specific for S. japonicum and able to detect S. japonicum DNA in rabbit sera at 1 week p.i. Following administration of praziquantel, detection of S. japonicum DNA in rabbit sera became negative at 12 weeks post-treatment. These results demonstrated that LAMP was effective for early diagnosis of, and evaluation of therapy effectiveness for, S. japonicum infection. Both PCR and LAMP assays were then used to detect S. japonicum DNA in 30 serum samples from S. japonicum-infected patients and 20 serum samples from healthy persons. The percentage sensitivity of LAMP was 96.7%, whereas that of PCR was only 60%, indicating that LAMP was more sensitive than conventional PCR for clinical diagnosis of schistosomiasis cases in endemic areas. The established LAMP assay should provide a useful and practical tool for the routine diagnosis and therapeutic evaluation of human schistosomiasis.

A new ovine Babesia species transmitted by Hyalomma anatolicum anatolicum

The pathogenicity and morphology of a large Babesia species, Babesia sp. Xinjiang, are described here. The parasite has very low virulence for sheep, and caused no detectable clinical symptoms. Splenectomized sheep infected with the parasite showed mild fever and low parasitemia and would recover gradually. If splenectomized sheep were immuno-suppressed with dexamethasone, the parasitemia could reach 8.5%, and death occurred. A splenectomized calf could not be infected with the Babesia species. Paired parasites were the typical form of the Babesia species in erythrocytes and the average size of a pair of parasites was 2.42 (+/-0.35) microm x 1.06 (+/-0.22) microm. Merozoites were found in the gut, salivary gland, haemolymph, ovary and eggs of female Hyalomma anatolicum anatolicum engorged on sheep infected with the parasites. The results of experimental transmission showed that the larval, nymph and adult stages of H. a. anatolicum could transmit the Babesia species to sheep.