Many species of tsetse flies are infected with a virus that causes salivary gland hypertrophy (SGH) symptoms associated with a reduced fecundity and fertility. A high prevalence of SGH has been correlated with the collapse of two laboratory colonies of Glossina pallidipes and colony maintenance problems in a mass rearing facility in Ethiopia. Mass-production of Glossina species is crucial for tsetse control programmes incorporating the sterile insect technique (SIT), and therefore requires a management strategy for this virus.
During the last decade the Joint FAO/IAEA Insect Pest Control Sub-programme investigated different strategies to manage the salivary gland hypertrophy virus (SGHV) in G. pallidipes mass production colonies, and developed an efficient virus management strategy, which succeeded in controlling and eliminating the virus from the tsetse mass production facility in Kality, Ethiopia. The virus management strategy that was developed is based on a combination of using antiviral drugs (Valacyclovir at a dose of 300 µg/ml of blood) and a clean feeding system. In addition to these methods, regular monitoring for the prevalence of SGH by dissection and the confirmation of SGHV by PCR is strongly recommended. In certain cases when attempting to start a new colony from field collected flies a new procedure to avoid using virus infected material is recommended.
To facilitate the monitoring for SGH or the SGHV infections and to properly implement the virus management strategy using a combination of the antiviral drug and the clean feeding system, this step-by-step standard operation procedure (SOP) has been developed, based on current knowledge and experiences from large-scale production of G. pallidipes. This document provides useful information for both large and small scale rearing facilities to maintain tsetse flies free from SGHV infection.
This SOP is addressed to staff involved in tsetse rearing with sufficient education to recognize SGH symptoms, and with the ability to regularly monitor variations from normal “healthy” flies. Such variations include reproductive disturbances (reduced matings and egg production) and reduced longevity (premature mortalities and prolonged larviposition cycles). For some parts of this SOP, more sophisticated experience in molecular biology techniques is required to conduct virus diagnosis using the Polymerase Chain Reaction (PCR) method.