The tropical rat mite, Ornithonyssus bacoti, was identified in a colony of mutagenized and transgenic mice at a large academic institution. O. bacoti is an obligate, blood-feeding ectoparasite with an extensive host range. Although the source of the infestation was likely feral rodents, none were found in the room housing infested mice. We hypothesize that construction on the floor above the vivarium and compromised ceiling integrity within the animal room provided for vermin entry and subsequent O. bacoti infestation. O. bacoti infestation was eliminated by environmental decontamination with synthetic pyrethroids and weekly application of 7.4% permethrin-impregnated cotton balls to mouse caging for five consecutive weeks. Visual examination of the macroenvironment, microenvironment, and colony for 38 days confirmed the efficacy of treatment. We noted no treatment-related toxicities or effects on colony production.

Ectoparasitic arthropods and vector-borne infectious agents are global medical and veterinary public health concerns. Economic impact due to direct effects of infestation and disease transmission are significant. These problems are increased by development of arthropod resistance to insecticides/acaricides; drug resistance of vector-borne pathogens; and, lack of effective vaccines to prevent many of these diseases. There is much to be gained from understanding the complex array of immunological interactions occurring at the arthropod-host-pathogen interface. One application of that knowledge is the development of novel vaccines for the control of both ectoparasitic arthropods and the diseases they transmit. We now realize that blood-feeding arthropods are not simply flying or crawling hypodermic needles and syringes. Ectoparasitic arthropods are not passive partners in their relationships with the immune systems of their hosts. These clever invertebrates produce numerous pharmacologically active molecules that help them migrate through tissues of their hosts or to successfully obtain blood meals. Arthropod parasites stimulate a spectrum of host immune responses that could potentially impair development, reduce feeding success, or kill the ectoparasite. Not unexpectedly, arthropods have developed sophisticated arsenals of countermeasures that modulate or deviate host immune responses. Not only does arthropod modulation of host immunity facilitate survival in tissues or increase the likelihood of obtaining a blood meal, but it is increasingly recognized as a critical factor in pathogen transmission. Those countermeasures to host immune defenses are the topics of this review. Emphasis is placed on our current understanding of the molecular bases of those changes; the molecules responsible for host immunomodulation; contemporary approaches for studying these complex relationships; and, the potential for using this information to develop innovative vaccine-based control strategies.

We report observations on infestations with the tick, Amblyomma triguttatum, in soldiers who were bivouacked in two areas near Perth; 34% of 175 persons were infested with varying stages of the ectoparasite. Most persons were infested with only one tick but some troops had multiple infestations. Local skin reactions to tick-bites were frequent; they usually developed 24-48 h after removal of the tick and may indicate delayed hypersensitivity reactions. A small number of persons developed secondary bacterial infections. Management and prevention of these infestations is reviewed briefly.

Immune reactivity stimulated by ectoparasites and other arthropods has received increased attention in recent years. It is clear that a broad range of host responses are elicited, and immune effector mechanisms appear to be active in limiting infestation with blood-feeding arthropods. Host immune responsiveness appears to be altered as a consequence of infestation by certain arthropods, and the impact of these alterations on vector-borne pathogen transmission remains to be determined. Successful techniques have been developed by a number of investigators for the artificial induction of resistance to blood-feeding arthropods. These areas are examined in this paper.