Understanding the Spread and Immune Response to a Blood Parasite in Horses

Greg Howard
6th July, 2024

Understanding the Spread and Immune Response to a Blood Parasite in Horses

This widespread tick infestation on the limbs, thighs, and tail is a key clinical sign that was strongly correlated with infection by the protozoan parasite Theileria equi in the horses under investigation.

Image adapted from: Ramadan et al. / CC BY (Source)

Key Findings

  • The study by Cairo University identified specific tick species (H. anatolicum, H. marginatum, and R. annulatus) as vectors for Theileria equi in horses in Egypt
  • T. equi infection in horses significantly increases oxidative stress markers (CAT, GPx, MDA, and SOD), correlating with parasitemia levels
  • There is a notable correlation between parasitemia levels and the expression of immune response genes (IFN-gamma, TGF-β1, and IL-1β) in infected horses
Equine piroplasmosis is a tick-borne disease affecting horses, caused by protozoan parasites such as Theileria equi (T. equi). This disease is not fully understood, particularly in terms of pathogenicity, prophylaxis, host immune response, and specific vectors. Accurate identification of the parasite vector is crucial for developing effective control measures. A recent study conducted by Cairo University[1] aimed to address this gap by identifying specific tick species acting as vectors for T. equi and examining the immune response in infected horses. The study focused on morphologically identifying two Hyalomma species (H. anatolicum and H. marginatum) and one Rhipicephalus annulatus (R. annulatus) at the species level. Identification was followed by phylogenetic analysis using the neighbor-joining method based on the cytochrome oxidase subunit 1 (COXI) gene. T. equi was diagnosed from infected blood samples and crushed tick species using conventional PCR. Phylogenetic analysis based on the amplification of the 18S rRNA gene was also conducted, with sequence data registered in GenBank under specific accession numbers. The results demonstrated that T. equi infection significantly increases oxidative stress markers (CAT, GPx, MDA, and SOD) in horses, correlating with parasitemia levels. Additionally, there was a notable correlation between parasitemia levels and the expression of immune response infection genes (IFN-gamma, TGF-β1, and IL-1β cytokines) in infected horses compared to non-infected equines. Common symptoms of T. equi infection included intermittent fever, enlarged lymph nodes, and tick infestation. This study builds on previous research on vector-borne diseases in equines and other animals in Egypt. For instance, a study on equine vector-borne diseases (EVBDs) identified various pathogens in ticks and flies collected from horses and donkeys, including Theileria equi and a new Theileria species[2]. Another study focused on ticks infesting cattle in Egypt, revealing the presence of multiple pathogens, including Theileria annulata and Anaplasma marginale[3]. These studies highlight the diversity of tick-borne pathogens in Egypt and underscore the importance of accurate vector identification for disease control. The current study expands on these findings by specifically identifying the tick species responsible for transmitting T. equi in horses and examining the immune response in infected animals. The use of phylogenetic analysis based on the COXI gene and 18S rRNA gene provided precise identification of the tick species and the parasite, respectively. This methodological approach ensures accurate vector identification, which is essential for developing targeted control measures. The study's findings on the immune response in infected horses are particularly significant. The observed increase in oxidative stress markers and the correlation with parasitemia levels provide insights into the pathogenic mechanisms of T. equi. Additionally, the correlation between parasitemia levels and the expression of immune response genes highlights the impact of the infection on the host's immune system. In conclusion, this study by Cairo University provides valuable insights into the vectors and immune response associated with T. equi infection in horses. By accurately identifying the tick species responsible for transmitting the parasite and examining the host's immune response, the study contributes to the development of effective control measures for equine piroplasmosis. These findings, in conjunction with previous research on vector-borne diseases in Egypt, underscore the importance of accurate vector identification and highlight the need for continued research in this area.

GeneticsBiochemAnimal Science

References

Main Study

1) Molecular and immunological studies on Theileria equi and its vector in Egypt

Published 5th July, 2024

https://doi.org/10.1007/s10493-024-00933-4

Related Studies

2) Molecular characterization of some equine vector-borne diseases and associated arthropods in Egypt.

https://doi.org/10.1016/j.actatropica.2021.106274

3) Tick species identification and molecular detection of tick-borne pathogens in blood and ticks collected from cattle in Egypt.

https://doi.org/10.1016/j.ttbdis.2021.101676


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