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Managing hytrosavirus infections in Glossina pallidipes colonies: feeding regime affects the prevalence of salivary gland hypertrophy syndrome.

Abd-Alla AM, Kariithi HM, Mohamed AH, Lapiz E, Parker AG, Vreysen MJ - PLoS ONE (2013)

Bottom Line: Implementation of a "clean feeding" regime (fresh blood offered to each set of flies so that there is only one feed per membrane), instead of the regular feeding regime (several successive feeds per membrane), was among the proposed approaches to reduce GpSGHV infections.We developed a new clean feeding approach applicable to large-scale tsetse production facilities using existing resources.The results indicate that implementing this approach is feasible and leads to a significant reduction in virus load from 10(9) virus copies in regular colonies to an average of 10(2.5) and eliminates the SGH syndrome from clean feeding colonies by28 months post implementation of this approach.

View Article: PubMed Central - PubMed

Affiliation: Insect Pest Control Laboratory, Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture, Vienna, Austria. a.m.m.abd-alla@iaea.org

ABSTRACT
Many species of tsetse flies are infected by a virus that causes salivary gland hypertrophy (SGH) syndrome and the virus isolated from Glossina pallidipes (GpSGHV) has recently been sequenced. Flies with SGH have a reduced fecundity and fertility. Due to the deleterious impact of SGHV on G. pallidipes colonies, several approaches were investigated to develop a virus management strategy. Horizontal virus transmission is the major cause of the high prevalence of the GpSGHV in tsetse colonies. Implementation of a "clean feeding" regime (fresh blood offered to each set of flies so that there is only one feed per membrane), instead of the regular feeding regime (several successive feeds per membrane), was among the proposed approaches to reduce GpSGHV infections. However, due to the absence of disposable feeding equipment (feeding trays and silicone membranes), the implementation of a clean feeding approach remains economically difficult. We developed a new clean feeding approach applicable to large-scale tsetse production facilities using existing resources. The results indicate that implementing this approach is feasible and leads to a significant reduction in virus load from 10(9) virus copies in regular colonies to an average of 10(2.5) and eliminates the SGH syndrome from clean feeding colonies by28 months post implementation of this approach. The clean feeding approach also reduced the virus load from an average of 10(8) virus copy numbers to an average of 10(3) virus copies and SGH prevalence of 10% to 4% in flies fed after the clean fed colony. Taken together, these data indicate that the clean feeding approach is applicable in large-scale G. pallidipes production facilities and eliminates the deleterious effects of the virus and the SGH syndrome in these colonies.

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Effect of long-term clean feeding system on SGH prevalence in the Seibersdorf Tororo G. pallidipes colonies by fly dissection.The flies were randomly selected at different time points from the different colonies after implementation of the clean feeding system and dissected to determine status of the salivary glands. Numbers between brackets are the mean of SGH prevalence percentage; lines are Loess smoothed regressions.
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pone-0061875-g003: Effect of long-term clean feeding system on SGH prevalence in the Seibersdorf Tororo G. pallidipes colonies by fly dissection.The flies were randomly selected at different time points from the different colonies after implementation of the clean feeding system and dissected to determine status of the salivary glands. Numbers between brackets are the mean of SGH prevalence percentage; lines are Loess smoothed regressions.

Mentions: The dissection results presented in Figure 3 show that the prevalence of the SGH syndrome in the CFC-1 was significantly reduced over the experimental period. Within 6 months of the implementation of the clean feeding regime, the SGH prevalence was reduced from 5–10% (the normal average prevalence in the Seibersdorf Tororo colony before treatment) to an average of 2.9%, irrespective of the age of the flies. After 11 months, the prevalence was further reduced to 2.3%, and SGH was completely eliminated in CFC-1 after 28 months. A similar trend was observed in the CFC-2 colony (Figure 3). In the NFC colony, there was a temporary increase in SGH prevalence to 24% during the first 6 months (with some weekly units exhibiting a prevalence of up to 40%). After 11 months, the SGH prevalence in the NFC colony averaged 23.7%, (with an average prevalence of ∼ 50% in younger flies (0–20 days old)). This rise in SGH prevalence was presumably due to the NFC flies being exposed to virus in the blood from emergence giving greater time and opportunity for infection. It is not clear if teneral flies are more susceptible to infection than older flies. However, after 28 months of the experiment, the SGH prevalence in the NFC was significantly reduced to 3.6%This was much lower than the levels regularly seen in standard-fed G. pallidipes colonies. In addition, while the SGH prevalence in the NFC colony appeared to vary with fly age during the first year of the experimental period, the prevalence stabilized later irrespective of the age of the flies (Figure 3). It is presumed that the initial increase in SGH prevalence was due to the teneral flies of the NFC being exposed to virus from the CFC-1 and CFC-2 feeding before the virus level decreased in these colonies, and subsequently declined after the SGH prevalence in the CFCs had decreased leading to the low, stable age-specific rates observed in the NFC.


Managing hytrosavirus infections in Glossina pallidipes colonies: feeding regime affects the prevalence of salivary gland hypertrophy syndrome.

Abd-Alla AM, Kariithi HM, Mohamed AH, Lapiz E, Parker AG, Vreysen MJ - PLoS ONE (2013)

Effect of long-term clean feeding system on SGH prevalence in the Seibersdorf Tororo G. pallidipes colonies by fly dissection.The flies were randomly selected at different time points from the different colonies after implementation of the clean feeding system and dissected to determine status of the salivary glands. Numbers between brackets are the mean of SGH prevalence percentage; lines are Loess smoothed regressions.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3646844&req=5

pone-0061875-g003: Effect of long-term clean feeding system on SGH prevalence in the Seibersdorf Tororo G. pallidipes colonies by fly dissection.The flies were randomly selected at different time points from the different colonies after implementation of the clean feeding system and dissected to determine status of the salivary glands. Numbers between brackets are the mean of SGH prevalence percentage; lines are Loess smoothed regressions.
Mentions: The dissection results presented in Figure 3 show that the prevalence of the SGH syndrome in the CFC-1 was significantly reduced over the experimental period. Within 6 months of the implementation of the clean feeding regime, the SGH prevalence was reduced from 5–10% (the normal average prevalence in the Seibersdorf Tororo colony before treatment) to an average of 2.9%, irrespective of the age of the flies. After 11 months, the prevalence was further reduced to 2.3%, and SGH was completely eliminated in CFC-1 after 28 months. A similar trend was observed in the CFC-2 colony (Figure 3). In the NFC colony, there was a temporary increase in SGH prevalence to 24% during the first 6 months (with some weekly units exhibiting a prevalence of up to 40%). After 11 months, the SGH prevalence in the NFC colony averaged 23.7%, (with an average prevalence of ∼ 50% in younger flies (0–20 days old)). This rise in SGH prevalence was presumably due to the NFC flies being exposed to virus in the blood from emergence giving greater time and opportunity for infection. It is not clear if teneral flies are more susceptible to infection than older flies. However, after 28 months of the experiment, the SGH prevalence in the NFC was significantly reduced to 3.6%This was much lower than the levels regularly seen in standard-fed G. pallidipes colonies. In addition, while the SGH prevalence in the NFC colony appeared to vary with fly age during the first year of the experimental period, the prevalence stabilized later irrespective of the age of the flies (Figure 3). It is presumed that the initial increase in SGH prevalence was due to the teneral flies of the NFC being exposed to virus from the CFC-1 and CFC-2 feeding before the virus level decreased in these colonies, and subsequently declined after the SGH prevalence in the CFCs had decreased leading to the low, stable age-specific rates observed in the NFC.

Bottom Line: Implementation of a "clean feeding" regime (fresh blood offered to each set of flies so that there is only one feed per membrane), instead of the regular feeding regime (several successive feeds per membrane), was among the proposed approaches to reduce GpSGHV infections.We developed a new clean feeding approach applicable to large-scale tsetse production facilities using existing resources.The results indicate that implementing this approach is feasible and leads to a significant reduction in virus load from 10(9) virus copies in regular colonies to an average of 10(2.5) and eliminates the SGH syndrome from clean feeding colonies by28 months post implementation of this approach.

View Article: PubMed Central - PubMed

Affiliation: Insect Pest Control Laboratory, Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture, Vienna, Austria. a.m.m.abd-alla@iaea.org

ABSTRACT
Many species of tsetse flies are infected by a virus that causes salivary gland hypertrophy (SGH) syndrome and the virus isolated from Glossina pallidipes (GpSGHV) has recently been sequenced. Flies with SGH have a reduced fecundity and fertility. Due to the deleterious impact of SGHV on G. pallidipes colonies, several approaches were investigated to develop a virus management strategy. Horizontal virus transmission is the major cause of the high prevalence of the GpSGHV in tsetse colonies. Implementation of a "clean feeding" regime (fresh blood offered to each set of flies so that there is only one feed per membrane), instead of the regular feeding regime (several successive feeds per membrane), was among the proposed approaches to reduce GpSGHV infections. However, due to the absence of disposable feeding equipment (feeding trays and silicone membranes), the implementation of a clean feeding approach remains economically difficult. We developed a new clean feeding approach applicable to large-scale tsetse production facilities using existing resources. The results indicate that implementing this approach is feasible and leads to a significant reduction in virus load from 10(9) virus copies in regular colonies to an average of 10(2.5) and eliminates the SGH syndrome from clean feeding colonies by28 months post implementation of this approach. The clean feeding approach also reduced the virus load from an average of 10(8) virus copy numbers to an average of 10(3) virus copies and SGH prevalence of 10% to 4% in flies fed after the clean fed colony. Taken together, these data indicate that the clean feeding approach is applicable in large-scale G. pallidipes production facilities and eliminates the deleterious effects of the virus and the SGH syndrome in these colonies.

Show MeSH
Related in: MedlinePlus