Machupo virus, the cause of
Bolivian hemorrhagic fever, is a highly lethal
viral hemorrhagic fever with no Food and Drug Administration-approved
vaccines or
therapeutics. This study evaluated the guinea pig as a model using the Machupo virus-Chicava strain administered via
aerosol challenge. Guinea pigs (Cavia porcellus) were serially sampled to evaluate the temporal progression of
infection, gross and histologic lesions, and sequential changes in serum chemistry and hematology. The incubation period was 5 to 12 days, and complete blood counts revealed
leukopenia with
lymphopenia and
thrombocytopenia. Gross pathologic findings included congestion and
hemorrhage of the gastrointestinal mucosa and serosa, noncollapsing lungs with fluid exudation, enlarged lymph nodes, and progressive pallor and friability of the liver. Histologic lesions consisted of foci of degeneration and cell death in the haired skin, liver, pancreas, adrenal glands, lymph nodes, tongue, esophagus, salivary glands, renal pelvis, small intestine, and large intestine. Lymphohistiocytic
interstitial pneumonia was also present.
Inflammation within the central nervous system, interpreted as nonsuppurative
encephalitis, was histologically apparent approximately 16 days postexposure and was generally progressive. Macrophages in the tracheobronchial lymph node, on day 5 postexposure, were the first cells to demonstrate visible
viral antigen.
Viral antigen was detected throughout the lymphoid system by day 9 postexposure, followed by prominent spread within epithelial tissues and then brain. This study provides insight into the course of
Machupo virus infection and supports the utility of guinea pigs as an additional animal model for
vaccine and therapeutic development.