Ultrastructural Changes in the Milk Gland of Tsetse Glossina morsitans centralis (Diptera; Glissinidae) Female Infected by a DNA Virus.

Milk glands, dissected out and collected from Glossina morsitans centralis (Machado) females, artificially inoculated at the third-instar larval stage with a virus suspension obtained from hypertrophied salivary glands of wild-caught virus-infected Glossina pallidipes (Austen), were processed for routine electron microscopy and examined for pathological changes. They were compared to milk glands dissected out from normal female G.m. centralis at the same stage of pregnancy cycle. Upon dissection there were notable physical differences between control and virus-infected milk glands. Histologically, some areas of the gland developed severe degeneration while other areas developed less severe pathological changes. Ultrastructural studies revealed the presence of virus particles in the secretory cell nuclei and within the cytoplasm and also showed that the nucleus was the site of virogenesis with mature naked virions budding through the nuclear membrane and acquiring the envelope from the nuclear membrane. Milk glands from normal females showed normal cellular organization of the secretory cells and secretory vesicles around the collecting gland lumen. The demonstration of virus particles in the secretory cell nuclei and cytoplasm suggests another mode of transmission of the virus from the infected mother to the larva in utero.