CARE, MAINTENANCE, AND EXPERIMENTAL INFECTION OF BITING MIDGES

Authors: Hunt, Gregg; Schmidtmann, Edward

Submitted to: The Biology of Disease Vector 2nd Edition
Publication Type: Book / Chapter
Publication Acceptance Date: 5/21/2004
Publication Date: 2/28/2005
Citation: Hunt, G.J., Schmidtmann, E.T. 2005. Care, maintenance, and experimental infection of biting midges. The Biology of Disease Vector 2nd Edition.

Interpretive Summary: Understanding pathogen-vector-host interactions is fundamental to the control of arthropod-borne diseases. Culicoides (Diptera: Ceratopogonidae) biting midges represent confirmed or suspected vectors of many disease agents among vertebrate hosts. Investigators conducting vector competence studies of biting midges have been limited by the small size and the difficulty of colonizing or maintaining these insects in the laboratory. Nevertheless, various species of Culicoides have been incriminated as vectors of helminths, protozoa, and viruses based on field or laboratory studies. The laboratory colonization and rearing of Culicoides sonorensis conducted at the Arthropod-borne Animal Diseases Research Laboratory (ABADRL) have been key to investigations concerning the role of this biting midge as a vector of several viral pathogens of veterinary importance in the U.S., notably the bluetongue (BTV) viruses, epizootic hemorrhagic disease viruses, and vesicular stomatitis viruses. This biting midge is the principal vector of the BTV viruses afflicting cattle, sheep, and wild ruminants in western and southern U.S. Bluetongue, an Office of International Epizooties List A animal disease, imposes morbidity and mortality in sheep, reproductive damage in cattle and sheep, and animal health restrictions for the international movement of breeding livestock and germplasm. Bluetongue disease is the most economically important arthropod-borne animal disease in the U.S. Culicoides sonorensis was colonized originally in 1956 to facilitate studies on vector competence for the BTV viruses and on methods for vector control. Thereafter, numerous colonies and transient populations of C. sonorensis have been started from field-collected larvae and pupae. Investigators have contributed improvements in the large-scale production and standardization of rearing techniques. Current production at the ABADRL is about 2½ million adults annually, and this species of Culicoides is the only ceratopogonid that is maintained continuously in prominent numbers at an insectary. For field and laboratory bionomics, the process of establishing and maintaining vector colonies is based upon the development of insectary design, environmental controls, rearing procedures, insectary equipment, and nutrition with an understanding of the field bionomics such as insect biology, behavior, habitat, and diet. The reproduction of certain field conditions has provided the foundation for the successful rearing of numerous short- and long-term colonies of C. sonorensis at the ABADRL. The success of our large-scale production of C. sonorensis has been attributed to the detailed procedures and specialized insectary equipment that have been developed over 4½ decades. However, the rearing procedures have proved unsuitable for initiating many new colonies from field populations collected throughout the U.S. Fundamental problems consist of insufficient blood-feeding rates and failure to mate during our laboratory conditions. Additional concerns include field-collected mud samples containing immature stages of other Diptera, possibility of naturally occurring insect pathogens, mortality caused by temperature variation, mortality evoked by excessive handling of adults, changes in genetic variability, and deviations in oral susceptibility during vector competence studies. During the colonization and routine maintenance of C. sonorensis, precautions must be taken to prevent both the escape of biting midges and the introduction of exogenous insects. Physical restrictions such as a double-screened vestibule at each entrance to a rearing room, the sealing of all openings and room penetrations (e.g., air handling, electrical, and plumbing), and numerous strategically placed insect light traps that serve as monitoring and abatement devices are used in each work area throughout the in

Technical Abstract: The laboratory colonization and rearing of Culicoides sonorensis (Diptera: Ceratopogonidae) conducted at the Arthropod-borne Animal Diseases Research Laboratory (ABADRL) have been key to investigations concerning the role of this biting midge as a vector of several viral pathogens of veterinary importance in the U.S., notably the bluetongue, epizootic hemorrhagic disease, and vesicular stomatitis viruses. Numerous colonies and transient populations of C. sonorensis have been started from field-collected larvae and pupae in which investigators have contributed improvements in the large-scale production and standardization of rearing techniques since 1956. Current production at the ABADRL is about 2½ million adults annually. The process of establishing and maintaining vector colonies is based upon the development of insectary design, environmental controls, rearing procedures, insectary equipment, and nutrition with an understanding of the field bionomics such as insect biology, behavior, habitat, and diet. The reproduction of certain field conditions has provided the foundation for the successful rearing of numerous short- and long-term colonies of C. sonorensis. However, insufficient blood-feeding rates and failure to mate during our laboratory conditions have prevented the establishment of various new colonies from field-collected populations. During the colonization and routine maintenance of C. sonorensis, precautions must be taken to prevent both the escape of biting midges and the introduction of exogenous insects. Furthermore, well established protocols and equipment are used to handle virus-infected C. sonorensis safely and securely during Biosafety Level 3 vector competence evaluations for oral susceptibility, intrathoracic inoculation, animal host transmission, or transovarial transmission. Investigators working with pathogen-infected arthropods must adhere to guidelines describing biosafety and arthropod security to preclude the exposure of laboratory personnel and to prevent the escape of hazardous pathogens or infected arthropods into the environment where domestic livestock, wildlife, or human populations may become endangered by an unintentional release.