Jianxun Luo

Ovine theileriosis in China : a new look at an old story

A fatal disease of sheep and goats in the northwestern part of China has in the past been reported to be due to Theileria lestoquardi. However, some characteristics of the causative agent are not in accordance with attributes ascribed to this parasite. We therefore determined the nucleotide sequence of the 18 small subunit ribosomal RNA (18S rRNA) gene of T. lestoquardi and the parasite identified in China and compared it with that of other Theileria and Babesia species. In the inferred phylogenetic tree, the 18S rRNA sequence of the Chinese parasite falls inside the clade consisting of Theileria species evidencing that it belongs to this genus. The 18S rRNA sequence of the Chinese parasite was found to be most closely related to Theileria buffeli and clearly divergent to T. lestoquardi, suggesting that it was a yet unrecognized Theileria species. The phylogenetic relationship of Theileria species infecting sheep and goats on the basis of their 18S rRNA gene structure was addressed. We report on the existence of at least two additional ovine and caprine piroplasm species, designated T. luwenshuni and T. uilenbergi.

Molecular survey and genetic identification of Anaplasma species in goats from central and southern China.

ABSTRACT Anaplasma species are obligate intracellular rickettsial pathogens that impact the health of humans and animals. Few studies have been carried out on Anaplasma infections in central and southern China. This study was conducted to determine the coinfection rates of Anaplasma ovis, A. bovis, and A. phagocytophilum from 262 field blood samples of goats in these regions. The average prevalences of single infection of A. ovis, A. bovis, and A. phagocytophilum were 15.3, 16.0, and 6.1%, respectively. Coinfection of A. ovis and A. bovis was dominant, with an infection rate of 27.1%. Coinfection of A. ovis and A. phagocytophilum was 1.9% and that of A. bovis and A. phagocytophilum was 4.2%. Three-pathogen coinfection was found in three of four investigated provinces with a prevalence between 0 and 5.3%. The accuracy of the PCR results was corroborated by sequencing. Analysis of the 16S rRNA gene sequences of A. bovis and A. phagocytophilum confirmed the presence of these pathogens at the investigated sites and indicated the possible genetic diversity of A. phagocytophilum. Field blood inoculation of experimental animals led to successful identification and observation of the morphological shapes of A. bovis in the infected monocytes of sheep. Phylogenetic study with msp4 sequences of A. ovis indicated that the A. ovis genotypes from sheep in the north differed from the genotypes of goats in the investigated sites.

Experimental transmission of Theileria sp. (China 1) infective for small ruminants by Haemaphysalis longicornis and Haemaphysalis qinghaiensis

The experimental transmission of a recently identified new Theileria (China 1) species pathogenic for sheep and goats in northern China is described. Haemaphysalis qinghaiensis nymphs and adults developed from larvae and nymph engorged on sheep infected with Theileria sp. (China 1) were able to respectively transmit the Theileria sp. to splenectomized sheep. Meanwhile, H. longicornis nymphs and adults developed from larvae and nymphs engorged on sheep infected with Theileria sp. (China 1) were also able to respectively transmit this new Theileria sp. (China 1) to splenectomized sheep. These experiments suggested that the Theileria sp. (China 1) could be transmitted by at least two species of Haemaphysalis sp. ticks, H. longicornis and H. qinghaiensis, and the mode of transmission is stage to stage.

Phylogenetic Position of Small‐Ruminant Infecting Piroplasms

Abstract:  Theileria and Babesia are tick‐transmitted protozoa that cause great economical losses in livestock. Recently, interest has risen in sheep‐infecting piroplasms and a number of previously unidentified pathogens were described, particularly in China. To address the phylogenetic relationship of Theileria and Babesia species infecting sheep, the complete sequences of the 18 S small subunit ribosomal RNA genes of a panel of piroplasm isolates, including T. lestoquardi, T. ovis, T. separata, B. ovis, B. motasi, B. crassa, and several novel species, were compared. The classification based on the established phylogenetic tree corresponded with traditional systematics and revealed that sheep/goat piroplasm species are of a polyphyletic origin. In addition, these studies revealed the existence of at least two novel sheep/goat piroplasm species, designated Theileria sp. (China 1) and Theileria sp. (China 2).

Transmission of an unidentified Theileria species to small ruminants by Haemaphysalis qinghaiensis ticks collected in the field

Abstract. The transmission of a recently identified Theileria species pathogenic for sheep and goats in northern China is described. Haemaphysalis qinghaiensis nymphs which had been collected from grass in epidemic areas were able to transmit this Theileria species to sheep. The pathogen was also transmitted to sheep and goats by three batches of adult ticks collected from grass, ticks collected when moving about on sheep and ticks which were found partially engorged on sheep or goats.

Molecular detection and characterization of Anaplasma spp. in sheep and cattle from Xinjiang, northwest China

BackgroundAnaplasmosis is caused by obligate intracellular bacteria in the genus Anaplasma. These bacterial pathogens are transmitted by ticks and impact both human and animal health. This study was conducted to determine the prevalence and molecular characterization of Anaplasma spp. in ruminants sampled in Xinjiang, northwest China.MethodsA survey was performed in August 2012 in rural areas of six counties in Xinjiang province. A total of 250 blood samples from ruminants were collected and tested for the presence of Anaplasma spp. by PCR. Positive samples were genetically characterized based on the 16S rRNA and msp4 genes.ResultsThe results showed a high prevalence of Anaplasma spp. in ruminants, with at least three different Anaplasma species detected (A. phagocytophilum, A. bovis and A. ovis). The mean prevalence of single infection with each species was 17.6% (A. phagocytophilum), 4.8% (A. bovis) and 40.5% (A. ovis). Coinfection occurred in 20 (8.0%) animals. Phylogenetic analysis of the 16S rRNA gene of A. bovis and A. phagocytophilum revealed a higher degree of genetic diversity for the latter. The results for A. ovis showed genotypic variation among geographic regions in China. In addition, a closely related isolate to the canine pathogen A. platys was identified in ruminants.ConclusionsThis survey revealed a high prevalence of Anaplasma sp. infections in sheep and cattle in the northwestern border regions of China, indicating the potential risk of transboundary disease.

Ticks of small ruminants in China

The importance of ticks and tick-borne diseases of small ruminants in China is discussed. Of the 109 species of ticks identified to date in China, 45 species infest small ruminants. Five species have been proved to be involved, or possibly involved, in the transmission of tick-borne diseases. Anaplasma ovis, Babesia motasi, Babesia ovis and two unidentified species of Theileria, have been recorded in small ruminants in China. The diseases caused by these organisms are widespread in China, causing great economic losses, estimated at approximately 70 million USD per annum. Anaplasmosis occurs from September to March in Inner Mongolia and during spring in other areas. Babesiosis and theileriosis occur in March to June in northwestern China. The vectors of A. ovis are Dermacentor nuttalli, Hyalomma asiaticum and Rhipicephalus pumilio. These three species of ticks do not appear to transmit A. ovis transstadially or transovarially, but rather through movement of partially engorged, infected adult ticks from A. ovis carrier animals. The vector ticks of the two species of Babesia have not been very well documented, but at least two species of Haemaphysalis are thought to transmit them. Haemaphysalis qinghaiensis transmits the two as yet unidentified species of Theileria transstadially. Priorities for future research on these diseases are summarised.

Haemaphysalis qinghaiensis ticks transmit at least two different Theileria species: one is infective to yaks, one is infective to sheep

Adult Haemaphysalis qinghaiensis ticks from Gannan area, where ovine theileriosis is prevalent but bovine theileriosis has not been reported, transmitted Theileria parasites to yaks and sheep. Blood from the infected yak contained Theileria parasites that were infective to yaks, but not sheep. In contrast, blood from the infected sheep did not contain Theileria parasites infective to yaks. These results suggested that the ticks from the Gannan area were infected with two species of Theileria one which specifically parasitises yaks, one which parasitises sheep. Both infections were more aggressive in splenectomised hosts as compared to intact host. Adult H. qinghaiensis ticks from Zhanjiachuan area, where ovine theileriosis is prevalent but where no yaks are raised, transmitted Theileria parasites to ovine, but not yaks. Taken together these results indicate that H. qinghaiensis ticks may be infected with two different Theileria species. The species infective for sheep could be related to the newly recognised, but not yet named, pathogen recently reported in small ruminants in China. The species infective for yaks appears to be benign and is morphologically similar to parasites of the Theileria sergenti/orientalis/buffeli group.

Detecting and differentiating Theileria sergenti and Theileria sinensis in cattle and yaks by PCR based on major piroplasm surface protein (MPSP).

Theileria sergenti and Theileria sinensis are closely related members of benign Theileria species found in cattle and yaks in China. They are morphologically indistinguishable. A polymerase chain reaction (PCR) targeting major piroplasm surface protein of T. sergenti and T. sinensis was developed in this study. The newly developed oligonucleotide primer set was able to specifically amplify the DNA of T. sinensis and in conjunction with primers for T. sergenti and these two species could be detected and distinguished. Specificity testing also revealed that there was no cross-reaction with the other tick-borne diseases Theileria annulata, Babesia ovata, Anaplasma marginale as well as bovine white blood cells. Phylogenetic analysis based on the MPSP gene sequences confirmed the specificity of PCR assays. The sensitivity of the methods was 0.1pg DNA for the T. sergenti PCR and 1pg DNA for T. sinensis PCR. Two hundred and thirty-six field blood samples from of cattle and yaks were collected from five different geographical regions in China where benign Theileria species have been found. T. sergenti was found in all five provinces but was absent from one county in Gansu Province. T. sinensis was only found in Gansu Province. In both counties in Gansu where the parasites co-existed, mixed infections were detected. Our results indicate that the PCR methods developed in this study are suitable for the detection and differentiation of T. sergenti and T. sinensis.

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.