Haemonchus contortus (Barber's pole worm or "BPW") is the nematode "nemesis" of small ruminant production systems in tropical and subtropical regions of the world. Its reputation derives from a combination of high fecundity and a short generational interval that provides an enviable developmental plasticity for adaptation or resistance to control measures. This review critically examines the historical and current literature on the host-parasite-environment interaction for H. contortus, particularly in sheep, to highlight changes in parasite distribution and ecology on pasture, changes to the seasonal inhibition of fourth stage larvae and the most appropriate models to identify protective responses and assess vaccines. The review also proposes pathways to bring host genetics to fruition and avenues where advances in the parasite genome may complement control measures.

Theileria are blood-borne intracellular protozoal parasites belonging to the phylum Apicomplexa. Previously considered a benign parasite in Australia, outbreaks of clinical disease resulting from Theileria orientalis genotypes have been reported in Australia since 2006. Since this time, outbreaks have become widespread in south-eastern Australia, resulting in significant adverse impacts on local dairy and beef industries. This paper provides the first investigation into the possible biological and mechanical vectors involved in the rapid spread of the parasite. To identify possible vectors for disease, ticks, biting flies and mosquitoes were collected within active outbreak regions of Gippsland, Victoria. Ticks were collected from cattle and wildlife, and mosquitoes and biting flies were collected in traps in close proximity to outbreak herds. Ticks were identified via DNA barcoding of the mitochondrial cytochrome oxidase I gene. Barcoded ticks were pooled according to species or phylogenetic group and tested for the presence of T. orientalis and the genotypes Ikeda, Chitose and Buffeli using real-time PCR. DNA barcoding and phylogenetic analysis identified ticks from the following species: Haemaphysalis longicornis, Ixodes holocyclus, Ixodes cornuatus, Ixodes hirsti, and Bothriocroton concolor. Additional Haemaphysalis, Ixodes and Bothriocroton spp. were also identified. Of the ticks investigated, only H. longicornis ticks from cattle carried theilerial DNA, with the genotypes Ikeda, Chitose and Buffeli represented. Mosquitoes collected in close proximity to outbreak herds included; Aedes camptorhynchus, Aedes notoscriptus, Coquillettidia linealis, Culex australicus, and Culex molestus. Low levels of T. orientalis Buffeli genotype were detected in some mosquitoes. The haematophagous flies tested negative. This is the first demonstration of a potential vector for T. orientalis in the current Australasian disease outbreak.

The intracellular protozoal parasite Theileria orientalis has rapidly spread across South-eastern Australia, substantially impacting local cattle industries since 2006. Haemaphysalis longicornis appears to be a biological vector in the endemic regions. Mechanical transfer of blood by biting arthropods, in colostrum or iatrogenic transmission though husbandry procedures is another possible mode of transmission. This study assesses the risk of these mechanical modes of transmission. Blood was collected from a T. orientalis Ikeda positive Angus steer, and was inoculated into the jugular vein of 9 calves in 3 treatment groups, each with 3 animals. Calves in Group 1 received 10 ml of cryopreserved blood, while those in Groups 2 and 3 received 1 ml (fresh blood) and 0.1 ml (cryopreserved), respectively. An additional three animals remained as negative controls and the donor calf was also followed as a positive control. Blood was collected over 3 months, and analysed via qPCR for the presence of the parasite. Samples of the sucking louse Linognathus vituli were collected opportunistically from calves 5 months after inoculation and tested for T. orientalis. For the colostral transmission study, 30 samples of blood and colostrum were collected from cows at calving in an endemic herd. These samples along with blood from their calves were tested by qPCR for T. orientalis and for antibodies to the major piroplasm surface protein (MPSP). Eight of the nine inoculated calves became positive for T. orientalis. The prepatent period of these infections was inversely correlated with inoculation dose. All negative control calves remained negative and the positive control calf remained positive. Samples of L. vituli tested positive for T. orientalis Ikeda, while some samples of colostrum were also shown to be qPCR and anti-MPSP positive. All calves in the colostral study tested qPCR negative although one was antibody-positive. T. orientalis is capable of being mechanically transferred by intravenous inoculation with small volumes of blood and is detectable up to 5 months post-infection. Animals infected by this means may play a significant role in the transmission of the disease by acting as asymptomatic carriers. Other modes of blood transfer, including biting arthropods and colostral transfer are also possible modes of disease transmission.

Background: The tick vectorRhipicephalus micropluswhich transmitsBabesiaspp. and rickettsial pathogens has not been reported in Kenya since 1998. More recently, the pathogenicBabesia bovishas been detected in cattle blood DNA. The status ofR. microplusin Kenya remains unknown. This study employed morphological and molecular tools to characterizeR. microplusoriginating from Kenya and assess the genetic relationships between Kenyan and other AfricanR. microplusgenotypes.Methods: Ticks were collected in south-eastern Kenya (Kwale County) from cattle and characterized to investigate the existence ofR. microplus. Genetic and phylogenetic relationships between the Kenyan and other annotatedR. microplusreference sequences was investigated by analysis of the cytochromecoxidase subunit 1 (cox1) gene. To further characterize Kenyan ticks, we generated low coverage whole genome sequences of twoR. microplus, oneR. decoloratusandR. appendiculatus. AB. bovisspecific TaqMan probe qPCR assay was used to detectB. bovisin gDNA fromR. microplusticks.Results: Occurrence ofR. micropluswas confirmed in Kwale County, Kenya. The KenyanR. microplus cox1 sequences showed very high pairwise identities (> 99%) and clustered very closely with reference AfricanR. microplussequences. We found a low genetic variation and lack of geographical sub-structuring among the Africancox1 sequences ofR. microplus. Four complete mitochondrial (mt) genomes for twoR. microplus, oneR. decoloratusand oneR. appendiculatuswere assembled from next generation sequence data. The mitochondrial genome sequences of the two KenyanR. microplusticks clustered closely with reference genome sequences from Brazil, USA, Cambodia and India formingR. microplusClade A. NoB. boviswas detected in the KwaleR. microplusDNA.Conclusions: These findings confirm the presence ofR. microplusin Kenya and suggest thatR. microplusClade A is prevalent in cattle in sub-Saharan Africa. These and other recent findings of widespread occurrence ofR. microplusin Africa provide a strong justification for urgent surveillance to determine and monitor the spread ofR. microplusand vector competence ofBoophilusticks forB. bovisin Africa, with the ultimate goal of strategic control.

This review addresses the research landscape regarding vaccines against scour worms, particularly Trichostrongylus spp. and Teladorsagia circumcincta. The inability of past research to deliver scour-worm vaccines with reliable and reproducible efficacy has been due in part to gaps in knowledge concerning: (i) host-parasite interactions leading to development of type-2 immunity, (ii) definition of an optimal suite of parasite antigens, and (iii) rational formulation and administration to induce protective immunity against gastrointestinal nematodes (GIN) at the site of infestation. Recent 'omics' developments enable more systematic analyses. GIN genomes are reaching completion, facilitating "reverse vaccinology" approaches that have been used successfully for the Rhipicephalus australis vaccine for cattle tick, while methods for gene silencing and editing in GIN enable identification and validation of potential vaccine antigens. We envisage that any efficacious scour worm vaccine(s) would be adopted similarly to "Barbervax TM" within integrated parasite management (IPM) schemes. Vaccines would therefore effectively parallel the use of resistant animals, and reduce the frequency of drenching and pasture contamination. These aspects of integration, efficacy and operation require updated models and validation in the field. The conclusion of this review outlines an approach to facilitate an integrated research program.

• Conditions for the optimal generation interval for the “bush tick”, Haemaphysalis longicornis, in Australia have been determined. • Stabilates containing infective sporozoites of Theileria orientalis ikeda were produced from ground-up ticks (GUTS) and salivary glands of H.longicornis. • Sporozoites of Theileria orientalis required around 3–5 days of tick feeding to mature in salivary glands before transmission occurred (like T.parva). • GUTS and salivary gland stabilates produced detectable infections with T.orientalis in naive calves around 3–4 weeks after inoculation. • This study confirms the final host status of H.longicornis for T.orientalis in Australia, facilitating research for prophylaxis and vector control.