Theileria orientalis Ikeda has caused an epidemic of bovine anemia and abortion across several U.S. states. This apicomplexan hemoparasite is transmitted by Haemaphysalis longicornis ticks; however, it is unknown if other North American ticks are competent vectors. Since the disease movement is largely determined by the host tick range(s), the prediction of the T. orientalis spread among U.S. cattle populations requires determination of additional competent tick vectors. Although Rhipicephalus microplus has mostly been eradicated from the U.S., outbreaks in populations occur frequently, and the U.S. remains at risk for reintroduction. Since R. microplus is a vector of Theileria equi and T. orientalis DNA has been detected in R. microplus, the goal of this study was to determine whether R. microplus is a competent vector of T. orientalis. Larval R. microplus were applied to a splenectomized, T. orientalis Ikeda-infected calf for parasite acquisition, removed as molted adults, and applied to two T. orientalis naïve, splenectomized calves for transmission. After 60 days, the naïve calves remained negative for T. orientalis by PCR and cytology. Additionally, T. orientalis was not detected in the salivary glands or larval progeny of acquisition-fed adults. These data suggest that R. microplus is not a competent vector of the U.S. T. orientalis Ikeda isolate.

Mycoplasma ovipneumoniae is a respiratory pathogen that impacts domestic sheep (Ovis aries; DS) and bighorn sheep (Ovis canadensis; BHS). BHS are reported to be more susceptible than DS to developing polymicrobial pneumonia associated with M. ovipneumoniae infection. Using formalin-fixed paraffin-embedded tissues, we performed a retrospective study investigating the pulmonary immune response of DS and BHS to M. ovipneumoniae infection. M. ovipneumoniae infected DS exhibited a more robust and well-organized BALT formation as compared to BHS. Digital analysis of immunohistochemical chromogen deposition in lung tissue was used to quantitate T cell marker CD3, B cell markers CD20 and CD79a, macrophage markers CD163 and Iba1, and cytokine IL-17. A significant interaction of species and infection status was identified for CD3, CD163, and IL-17. BHS had a greater increase in bronchiolar CD3 and bronchiolar and alveolar CD163 with infection, as compared to DS. BHS had an increase in bronchiolar associated lymph tissue (BALT) and alveolar IL-17 with infection, while these remained similar in DS regardless of infection status. IL-17 in respiratory epithelium of bronchi and bronchioles comparatively decreased in DS and increased in BHS with infection. These data begin to define the interspecies differential immune response to pulmonary M. ovipneumoniae infection in DS and BHS and provide the first investigations of respiratory epithelium-associated IL-17 in ovine.

The mycoplasmas represent a large and diverse group of bacteria, many of which are pathogens of humans and animals. Here, we describe a draft genome sequence of a novel Mycoplasma species. This novel Mycoplasma species has potential to cause false-positive PCR results for Mycoplasma ovipneumoniae , a respiratory-associated pathogen of ruminants.

Vector-borne pathogens commonly establish multistrain infections, also called complex infections. How complex infections are established, either before or after the development of an adaptive immune response, termed coinfection or superinfection, respectively, has broad implications for the maintenance of genetic diversity, pathogen phenotype, epidemiology, and disease control strategies. Anaplasma marginale , a genetically diverse, obligate, intracellular, tick-borne bacterial pathogen of cattle, commonly establishes complex infections, particularly in regions with high transmission rates.

Bighorn sheep (BHS) populations have been reported to experience high levels of morbidity and mortality following infection with Mycoplasma ovipneumoniae. This contrasts with the subclinical presentation in domestic sheep (DS). Understanding this difference requires baseline knowledge of pre- and post-infection immune responses of both species. The present study identifies differences in leukocyte phenotypes between adult BHS and DS before and after intranasal inoculation with 1 × 10⁸ Mycoplasma ovipneumoniae. Prior to inoculation, BHS were confirmed to have a higher abundance of leukocyte CD14 and serum concentrations of IL-36RA. In contrast, DS had a higher leukocyte abundance of CD16 in addition to previously observed integrin markers and CD172a, as well as greater serum TNF-α concentrations. Within 15 days of inoculation, BHS displayed signs of mild respiratory disease and M. ovipneumoniae DNA was detected on nasal swabs using a quantitative PCR; meanwhile, DS exhibited few to no clinical signs and had levels of M. ovipneumoniae DNA below the standard curve threshold. Immunologic markers remained relatively consistent pre- and post-inoculation in DS, while BHS demonstrated changes in the peripheral leukocyte expression of CD172a and CD14. Circulating serum IL-36RA decreased and CXCL10 increased within BHS. These findings highlight significant differences in cellular immunity between BHS and DS, raised and housed under similar conditions, prior to and following inoculation with M. ovipneumoniae.

Theileria orientalis Ikeda, an emerging U.S. bovine hemoparasite, causes anemia, abortion, ill-thrift, and occasionally death. While Haemaphysalis longicornis is the primary vector, it is possible that other U.S. ticks are capable of parasite transmission and may contribute to disease spread. Dermacentor variabilis is highly prevalent in the U.S., exhibits a similar geographical distribution to T. orientalis, and is a competent vector of the related parasite, Theileria equi. Herein, we conducted controlled acquisition and transmission studies using splenectomized calves to assess whether D. variabilis can transstadially transmit T. orientalis. D. variabilis nymphs were applied to an infected, splenectomized calf for parasite acquisition and subsequently incubated to molt into adults. Freshly molted adults were applied to two splenectomized T. orientalis-naïve calves to investigate parasite transmission. Calves were monitored for 59 days, and no evidence of parasite transmission was detected using PCR for the T. orientalis Ikeda major piroplasm surface protein gene, blood smear cytology, complete blood counts, or physical examination. Salivary glands from a subset of D. variabilis adults were assessed for T. orientalis using PCR, and the parasite was not detected. These findings support the conclusion that D. variabilis is not capable of transstadial transmission of the U.S. T. orientalis Ikeda isolate.