The Oriental Rat Flea
Common Name: Oriental Rat Flea Scientific Name: Xenopsylla cheopis (Rothschild) Class/Order/Family: Insecta/Siphonaptera/Pulicidae Metamorphosis: Complete
INTRODUCTION
This flea receives its common name of oriental rat from the fact that its favorite hosts are rats, especially the Norway rat which is thought to be of central Asian origin. This flea's greatest importance is that it is the principal vector of bubonic plague and murine typhus from rats to humans. Oriental rat fleas are of worldwide distribution and found throughout the United States, but most commonly in seaport areas; scarce in northern areas but found as far north as Washington, Minnesota, and New Hampshire.
RECOGNITION
Adults about 1/16" (2-2.5 mm) long. Body laterally flattened (side to side); wingless. Color reddish brown. Head with front rounded, ocular bristle inserted in front of eye; genal comb lacking. Pronotat comb lacking; mesopleuron (side of mesothorax) divided by a vertical rodlike thickening; thorax not reduced, dorsum (top) equal to or larger than 1 st abdominal segment. Abdominal terga (dorsal plates) 2-6 with a single row of bristles; spermatheca (internal sperm storage organ; towards rear of abdomen) dark-colored, visible through exoskeleton in alcohol collected specimens. In addition, antennae short, 3-segmented; ocalli lacking; legs long, coxae large, tarsi 5- segmented; usually jumping insects; mouthparts piercing-sucking with well-developed palps. Mature larvae about 1/8-1/4" (3-5.2 mm) long. Larvae whitish, slender, eyeless, and legless. With a well-developed head. Anal struts/hooks 2, small. With moderately long, backward-projecting hairs (setae) encircling each segment. Last abdominal segment (10th) with 3 ventrolateral hairs (setae). Description is same as for dog and cat fleas.
SIMILAR GROUPS
- Human flea (Pulax irritans) with rnesopleuron (side of mesothorax) not divided by a vertical thickening, and ocular bristle inserted below eye.
- Sticktight flea (Echicnophaga gallinacea) and Chigoe flea (Tunga penetrans) with front of head angular, dorsum (top) of thorax shorter than lst abdominal segment dorsum; in addition, sticktight flea with a group of spinuies (short spines) on inner side of hind coxas.
- Polygenis gwyni (family Rhopalopsyllidae) with 2 rows of bristles on typical abdominal segment.
BIOLOGY
Females lay 4-8 eggs after each blood meal. Eggs are sticky but usually fall off the host or are deposited in the nest. The minimum temperature for egg development is 54degreesF/12degreesC. Larvae usually feed on organic matter including droppings from adult fleas but cannot develop solely on a blood diet; they can also successfully develop solely on grain stored in grain sacks. Because the larvae lack a closing mechanism on their spiracies, they require high humidity for development and move to areas of high humidity. Exposure to 0% RH at 72degreesF/22degreesC for 24 hours is lethal but at 90% RH the lethal temperature is 97 degrees F / 36 degrees C. Larvae go through 3 molts and then pupate. Successful pupation and emergence requires 64-95degreesF/18-35degreesC and 60+% RH. Females emerge 3-4 days before males. If well fed, adults may live for a year or more in the lab, but probably only 2-4 weeks in the wild. The life cycle (egg to egg) can be completed in as few as 4-8 weeks.
HABITS
Unfed adults are attracted to light but fed adults shun light. Adults have responded positively to the odor from a favorable host at up to 12" (30 cm) and were able to distinguish it from nonhost species. Adults can jump as far as 94" (24 cm) horizontally and 4.3" (1 1 cm) vertically. The favorite host is the Norway rat (Rattus norvegicus (Berkenhout)), but the oriental rat flea is also found on the cofton rat (Sigmodon hispidus Say & Ord), roof rat (R. rattus Linnaeus), the house mouse (Mus musculus Linnaeus), cottontail rabbits (Sylvilagus spp.), and the California ground squirrel (Spermophilus ap.). Oriental rat fleas readily bite and feed on humans. The medical concern is that these fleas are the principal vector of both bubonic plague and murine typhus. The transmission is primarily from rats to humans although other wild host reservoirs of these disease organisms can be involved.