The role of pulmonary intravascular macrophages in the pathogenesis of African horse sickness.

This research paper discusses the role of pulmonary intravascular macrophages in African horse sickness, a disease associated with severe lung swelling or edema in horses and caused by an orbivirus. The study suggests that these macrophages may contribute to vascular changes by producing certain inflammatory chemicals.

Objectives and Methods of the Research

• The primary goal of this research was to evaluate the role of pulmonary intravascular macrophages (PIMs) in the development of pulmonary, or lung, microvascular changes in African horse sickness (AHS).
• The study was conducted by intravenously injecting five horses with a particular dosage of the AHS virus. Following this, viral replication patterns and subsequent changes, particularly in terms of oedema and alterations in pulmonary microvasculature, were observed and analysed.

Viral Replication and Physical Alterations

• The scientists found that the virus replicated in several types of cells including endothelial cells (cells lining the blood vessels), PIMs, interstitial macrophages (macrophages residing in spaces between other types of cells or tissues), and fibroblasts (cells producing collagen and other fibres).
• Apart from viral replication, they detected the occurrence of alveolar (pertaining to tiny air sacs in the lungs) and interstitial (relating to spaces between organs or tissues) oedema. This swell was a key characteristic of AHS.

Role of PIMs in AHS

• Investigation into the changes seen in pulmonary microvasculature, primarily the trapping of neutrophils (a type of white blood cell), the formation of platelet aggregates and fibrinous microthrombi, showed a strong correlation with alterations in endothelial cells and a high level of PIM activation.
• The findings suggest that PIMs, once activated by the presence and replication of the AHS virus, contribute to the vascular changes observed in this disease by releasing chemical inflammatory mediators, which are substances that prompt or mediate the inflammation response.