ARS | Publication request: Solidifying agent and processing of blood used for the larval diet affect screwworm (Diptera: Calliphoridae) life-history parameters

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2011
Publication Date: June 1, 2011
Citation: Chaudhury, M.F., Skoda, S.R., Sagel, A. 2011. Solidifying agent and processing of blood used for the larval diet affect screwworm (Diptera: Calliphoridae) life-history parameters. Journal of Economic Entomology. 104(3):1103-1107.

Interpretive Summary: Screwworms are mass reared using a semi-solid diet which consists of dry cow blood, poultry egg powder and a milk substitute mixed with a bulking/solidifying agent and water. All ingredients of this diet are imported and are expensive. To reduce the cost of mass production of screwworms we investigated the suitability of locally available fresh cow blood to replace the imported expensive dry blood. Fresh blood needs to be de-coagulated before it can be used in the diet. Therefore, tests were conducted to determine most suitable de-coagulation method. Screwworm larvae were reared using diets prepared with fresh cow blood treated with anticoagulant sodium citrate or EDTA, or mechanically defibrinated and mixed with either a gelling agent or cellulose fiber as the bulking/solidifying agent. For comparison, screwworm larvae are also reared in the standard diet prepared from dry blood. Weights of larvae and pupae, number of pupae per tray, fecundity, fertility, and adult emergence and survival were recorded. Most of these parameters from insects reared in diet with defibrinated blood were similar to those recorded from insects reared in standard diet. This suggests that dry blood can be replaced by fresh blood. There was a significant reduction in the weights of larvae and pupae that were reared in diets prepared with citrated blood and some reduction when diets with EDTA-treated blood were used. This indicates that use of chemical anti-coagulants is not suitable for larval growth and survival.

Technical Abstract: The current artificial diet for mass rearing screwworm, Cochliomyia hominivorax, (Coquerel) (Diptera: Calliphoridae) larvae is a semi-solid medium consisting of dry whole bovine blood, poultry egg powder and a milk substitute mixed with a bulking and solidifying agent and water. To reduce the mass rearing cost we continue to investigate the suitability of locally available inexpensive materials. Also, there is uncertainty of continually procuring spray-dried whole bovine blood from commercial manufacturers. We tested the suitability of fresh bovine blood as one of the dietary ingredients in the rearing medium. Fresh bovine blood requires de-coagulation prior to use in the screwworm diet; we determined the suitability of various de-coagulation methods. Diets were prepared with bovine blood treated with anticoagulants sodium citrate or EDTA (ethylene-diamine-tetra-acetic acid), or mechanically defibrinated blood and mixed with either a gelling agent or cellulose fiber as a bulking/solidifying agent compared with the standard diet prepared with spray-dried bovine blood. Larval and pupal weights, number of pupae per tray, fecundity, fertility, and adult emergence and survival were recorded. There was significant reduction in larval/pupal weights and number of pupae obtained from the diets prepared from citrated blood, indicating that the use of sodium citrate as anticoagulant is not suitable for larval growth and survival. EDTA-treated blood using the gel bulking agent showed significant reductions similar to citrated blood. EDTA treated blood with fiber bulking agent produced significantly better screwworms than citrated blood but inferior to the control. Defibrinated bovine blood produced screwworms that were similar to those reared in standard diet, indicating that the dry blood can be successfully replaced by fresh, defibrinated bovine blood.