Laura Krueger, Kiet Nguyen, Robert Velten, Stephen Bennett, Carrie Fogarty, Sokanary Sun and Robert Cummings
Orange County Vector Control District, 13001 garden grove Blvd, garden grove, CA, 92843, (714) 971-2421, [email protected]
ABSTRACT: The Orange County Vector Control District flea-borne typhus prevention and response program consists of two main components. The first component is an ecological investigation to determine neighborhood risk and the second component is a public education program. Results from the ecological investigation guide the geographic extent of the public education campaign.
INTRODUCTION
Orange County, California, has experienced a resurgence in human cases of flea-borne typhus. From 2006 to 2012, 85 suspected, probable and confirmed human cases of flea-borne typhus were reported to the Orange County Health Care Agency. Previous to 2006 no flea-borne typhus infections had been reported in Orange County since 1991. From 2006 to 2008, the Orange County Vector Control District (OCVCD) collaborated with the Centers for Disease Control, Division of Vector-borne Diseases, to investigate pathogen, vector and host relationships in Orange County for flea-borne rickettsiosis. Results from this collaborative study identified the suburban cycle of flea- borne typhus transmission (backyard wildlife - fleas
- humans) in Orange County (Eremeeva et al. 2012), similar to earlier findings in neighboring Los Angeles County (Civen and Ngo 2008). Three species of fleas commonly found on opossums, feral cats, raccoons, skunks, domestic cats and domestic dogs were found to harbor Rickettsia felis and/or R. typhi, the causative agents of flea-borne rickettsiosis (Table 1)
The most prevalent flea species in southern California, Ctenocephalides felis Bouche´, regularly infests backyard wildlife and companion cats and dogs and is an avid human biter. It is believed that backyard wildlife such as opossums, feral cats, raccoons and skunks maintain populations of C. felis in the environment (Adams 1970). Ctenocephalide felis then infests companion cats and dogs not currently on
table 1. Detection of
R. typhi and R. felis
DNA in Flea DNA Samples (Excerpt from Eremeeva et al. 2012)
flea control. The companion cats and dogs bring the fleas into the home environment where they bite and infect their owners with the causative agents of flea- borne rickettsiosis, Rickettsia felis and R. typhi (Table 1 - CDC, 2009, Eremeeva et al. 2012, Karpathy et al. 2009, Reif 2009). Humans become infected with R.
typhi through accidental contact with infected fleas and
their feces by inhalation or scarification into damaged skin (Azad 1990). R. felis and R. typhi are not known to cause illness in wildlife and/or pet cats and dogs, although R. felis has been identified from hepatic and renal tissue of opossums (Eremeeva et al. 2012).
OVERVIEW OF FLEA-BORNE TYPHUS AND RESPONSE PROGRAM
In response to this increasing disease burden, OCVCD established a flea-borne typhus prevention and response program consisting of two main components: an ecological investigation to determine neighborhood risk through surveillance of backyard wildlife and fleas and a public education program. Results from the ecologic investigation guide the geographic extent of the public education campaign. The ecological investigation consists of the following elements:
1) Inspection for backyard wildlife – opossums, feral cats, raccoons, skunks, rats, mice.
2) Inspection for conditions conducive to infestations such as harborage, food and water sources. 3) Inspection of companion cats and/or dogs for
evidence of flea infestations;.
4) Inspection for evidence of flea infestations on property.
5) Trapping of opossums for determination of the flea index (# fleas/animal) as an indication of neighborhood risk.
From 2006 - 2012, OCVCD trapped 169 opossums associated with flea-borne typhus exposure sites. The average flea index was 53.51 fleas per opossum with a range of 0 - 501 fleas per animal. In neighborhoods where the flea index is significantly higher per opossum trapped, the geographic extent of the neighborhood notification is increased.
OCVCD’s public education campaign occurs in/around known flea-borne typhus exposure sites. OCVCD staff goes door-to-door in the area directly adjacent to the flea-borne typhus exposure site providing information on the disease. If conditions are conducive to backyard wildlife, OCVCD educates residents on ways to make their properties less attractive to these animals. Residents are advised to put their pet animals on flea control and/or contact a structural pest control company for environmental flea control. When appropriate, properties with significant issues, such as hoarding, are referred to other governmental agencies for assistance.
REFERENCES CITED
Adams, W. H., R. W. Emmons, and J. E. Brooks. 1970. The changing ecology of murine (endemic) typhus in Southern California. Am. J. Trop. Med. Hyg. 19: 311-318.
Azad, A. F. 1990. Epidemiology of Murine Typhus. Annu. Rev. Entomol. 35: 553-569.
Centers for Disease Control and Prevention. 2009. Outbreak of Rickettsia typhi infection - Austin, Texas, 2008. MMWR 58: 1267-1270.
Civen, R. and V. Ngo. 2008. Murine typhus: an unrecognized suburban vectorborne disease. Clin. Infect. Dis. 46: 913-918.
Eremeeva S.E, S. E. Karpathy, L. Krueger, E. K. Hayes, A. M. Williams, Y. Zaldivar, S. Bennett, R. Cummings, A. Tilzer, R. K. Velten, N. Kerr, G. A. Dasch, R. Hu . 2001. Two pathogens and one disease: detection and identification of flea-borne rickettsiae in areas endemic for murine typhus in California. J. Med. Entomol. 49: 1485-1494. Karpathy, S. E., E. K. Hayes, A. M. Williams, R. Hu,
L. Krueger, S. Bennett, A. Tilzer, R. K. Velten, N. Kerr, W. Moore, and M. E. Eremeeva. 2009. Detection of Rickettsia felis and Rickettsia typhi in an area of California endemic for murine typhus. Clin. Microbiol. Infec. 15 Suppl 2: 218-219. Reif K.E., K.H. Macalasu. 2009. The ecology of
Rickettsia felis: A Review. J. Med. Entomol.