Hoplopsyllus Anomalus Research Articles

Prevalence and Seasonality of Fleas Associated With California Ground Squirrels and the Potential Risk of Tularemia in an Outdoor Non-Human Primate Research Facility.

Ectoparasites at primate research centers may be difficult to control, e.g. without exposing non-human primates (NHPs) to toxicants, but their impact on NHP health is poorly understood. In 2010, there was an epizootic of tularemia at the California National Primate Research Center (CNPRC) in Yolo County, California that resulted in 20 confirmed and suspect clinical cases in outdoors housed rhesus macaques (Macaca mulatta [Zimmermann]) and a 53% seroprevalence in the southern section of the colony. We studied ectoparasite burdens at the CNPRC in order to understand possible conditions at the time of the epizootic and provide data for the management of ectoparasites for the future. In 2015, we recorded 52 California ground squirrel (Otospermophilus beecheyi [Richardson]) burrow systems in the southern colony and collected 560 fleas. The largest number of fleas (n = 184) was collected in October and the most common species were Hoplopsyllus anomalus (Baker) (n = 331), Oropsylla montana (Baker) (n = 158), Echidnophaga gallinacea (Westwood) (n = 60), and Ctenocephalides felis (Bouché) (n = 11), all of which are opportunistically anthropophilic. Free, non-host-associated fleas included 12 H. anomalus, 9 C. felis, 6 O. Montana, and 1 E. gallinacea. We collected 1 H. anomalus from a rhesus macaque. Our results suggest a high potential for the rapid spread of zoonotic infectious diseases via flea transmission in primate facilities with ground squirrels and that flea control measures should be given a high priority.

Distribution and Diversity of Bartonella washoensis Strains in Ground Squirrels from California and Their Potential Link to Human Cases.

We investigated the prevalence of Bartonella washoensis in California ground squirrels (Otospermophilus beecheyi) and their fleas from parks and campgrounds located in seven counties of California. Ninety-seven of 140 (69.3%) ground squirrels were culture positive and the infection prevalence by location ranged from 25% to 100%. In fleas, 60 of 194 (30.9%) Oropsylla montana were found to harbor Bartonella spp. when screened using citrate synthase (gltA) specific primers, whereas Bartonella DNA was not found in two other flea species, Hoplopsyllus anomalus (n = 86) and Echidnophaga gallinacea (n = 6). The prevalence of B. washoensis in O. montana by location ranged from 0% to 58.8%. A majority of the gltA sequences (92.0%) recovered from ground squirrels and fleas were closely related (similarity 99.4-100%) to one of two previously described strains isolated from human patients, B. washoensis NVH1 (myocarditis case in Nevada) and B. washoensis 08S-0475 (meningitis case in California). The results from this study support the supposition that O. beecheyi and the flea, O. montana, serve as a vertebrate reservoir and a vector, respectively, of zoonotic B. washoensis in California.

New Flea (Siphonaptera) Record For Heermann's Kangaroo Rat (Dipodomys heermanni), San Luis Obispo County, California

ABSTRACT. Three Heermann's kangaroo rats (Dipodomys heermanni LeConte 1853) from San Luis Obispo County, California, were examined for ectoparasites. Two species of fleas were found, Meringis cummingi (C. Fox 1926) and Hoplopsyllus anomalus (Baker 1904). While M. cummingi has been reported frequently from this host (Dorman 1969, Eads et al. 1987), occurrence of H. anomalus on D. heermanni has not been reported before and represents a new host record.

Seasonal and among-site variation in the occurrence and abundance of fleas on California ground squirrels (Otospermophilus beecheyi)

An improved understanding of the ecology of fleas on California ground squirrels, Otospermophilus beecheyi, is warranted given the role of fleas in the transmission, and perhaps persistence, of the plague-causing bacterium Yersinia pestis. We sampled O. beecheyi on a seasonal basis from three study sites, each representing a different land use type (preserve, pasture, and agriculture) in the San Joaquin Valley, CA. Overall, the abundance of fleas on squirrels was greatest in spring at the preserve site, in summer at the agriculture and pasture sites, and in winter at the pasture site. Hoplopsyllus anomalus, the species most frequently found on squirrels, was most abundant in spring at the preserve site and in summer at the agriculture and pasture sites. Oropsylla montana was most abundant in winter at the pasture site and on adult squirrels. Echidnophaga gallinacea was most abundant in fall on juvenile squirrels at the preserve site. All three flea species we encountered are known to be potential vectors of Y. pestis. Future efforts to predict flea species occurrence and abundance (and plague risk) at sites of concern should consider seasonal microclimatic conditions and the potential influence of human land use practices.

Laboratory techniques for rearing the fleas (Siphonaptera: Ceratophyllidae and Pulicidae) of California ground squirrels (Rodentia: Sciuridae) using a novel nest box.

Three species of fleas, Oropsylla montana (Baker), Hoplopsyllus anomalus (Baker), and Echidnophaga gallinacea (Westwood), occur seasonally on the California ground squirrel, Spermophilus beecheyi (Richardson). Few studies have focused on the biology and ecology of these fleas despite their importance in the epidemiology of sylvatic plague. To best duplicate a natural parasite-host relationship in the laboratory, a novel nest box was developed that facilitated housing wild-caught S. beecheyi, was conducive to rearing fleas, and met modern standards for laboratory animal hygiene. This flexible system allowed adult fleas with different feeding strategies to be colonized successfully while providing sufficient flea eggs for both colony maintenance and biological research. The techniques described could be adapted to work with other species of rodents and their fleas.

Use of orally administered chitin inhibitor (lufenuron) to control flea vectors of plague on ground squirrels in California.

The efficacy of orally administered lufenuron, a chitin inhibitor, to control fleas on California ground squirrels, Spermophilus beecheyi (Richardson), was evaluated during a 2-yr study in Santa Barbara County, CA. Results demonstrated that use of a host-targeted feed cube containing lufenuron was effective in significantly reducing the burden of Oropsylla montana (Baker) and Hoplopsyllus anomalus (Baker) fleas on ground squirrels. A flea index that indicated a mean number of fleas per squirrel of 10.0 decreased to 1.3 after 2 treatments in season 1, and to 0.7 and 0.2 after the 3rd and 4th treatments, respectively, in season 2. A cost comparison of this new method compared with a traditional reactive, emergency, insecticide-based plague control program demonstrated a cost reduction of approximately 90%. The results of this study indicated that a lufenuron feed cube was an effective, cost-saving, and proactive technique for controlling fleas on California ground squirrels, and thus reducing the risk of disease transmission in plague endemic regions.

Factors affecting the seasonal abundance of ground squirrel and wood rat fleas (Siphonaptera) in San Diego County, California.

Abiotic and biotic factors affecting the seasonal abundance of 3 species of sylvatic fleas on their hosts were examined at 7 sites in San Diego County, California. Indices for Oropsylla (Diamanus) montana (Baker) were usually highest on Spermophilus beecheyi nudipes (Huey) when < 18.4 degrees C (October-December), whereas those for Hoplopsyllus anomalus (Baker) were highest when > 18.4 degrees C (July-September). O. montana was affected most by ambient temperature (inversely for the coastal site [134 m] and directly for most mountain sites [> 1,183 m]). O. montana was affected most (directly) by relative humidity at the inland valley site, which concurs with this flea being most abundant in other areas during periods yielding higher relative humidties and moderate ambient temperatures. H. anomalus was influenced most (directly) by ambient temperature at lower sites (< 1,183 m) and by host activity at higher ones (> 1,456 m). Usually nonrandom distribution findings, when indices for each squirrel flea were higher on some hosts, indicate that flea numbers are correspondingly higher in some nests and burrows because of more favorable microconditions. Data also indicated that plague may persist at higher sites in southern California or in other areas where climatic conditions permit increased and prolonged interactions between more abundant O. montana and its host during spring through summer. Whereas, plague may have less chance of persisting at lower sites because these interactions are decreased and shortened during the warmer months. Squirrels may become infected with plague following hibernation and again when reoccupying colonial burrows. The flea Orchopeas sexdentatus was affected most (inversely) by relative humidity at a coastal site, with higher indices occurring on fewer Neotoma lepida Thomas and on more abundant Neotoma fuscipes macrotis Thomas during colder months. Such increased flea/Neotoma fuscipes Baird activity at lower sites may favor plague amplification during the winter which may involve ground squirrels and other rodents in the spring.

Fleas (Siphonaptera) Infesting Giant Kangaroo Rats (Dipodomys ingens) on the Elkhorn and Carrizo Plains, San Luis Obispo County, California

The giant kangaroo rat, Dipodomys ingens (Merriam), has a limited distribution in the San Joaquin Valley, CA. Because of reductions in its geographic range, largely resulting from humans, the species was listed as an endangered species in 1980 by the California Fish and Game Commission. As part of a study of the community ecology of southern California endangered species, including D. ingens, we were able to make flea collections from the rats when they were trapped and marked for population studies. All but one of the fleas collected from the D. ingens in this study were Hoplopsyllus anomalus, a flea normally associated with ground squirrels (Sciuridae). It has been suggested that giant kangaroo rats fill the ground squirrel niche within their range. Our data indicate that this role includes a normal association with Hoplopsyllus anomalus.

Field studies of reservoirs and vectors of sylvatic plague at Fort Hunter Liggett, California.

Vectors and reservoirs of sylvatic plague were studied at Fort Hunter Liggett, Monterey County, California, from November 1974 to September 1976, with particular reference to the California Ground Squirrel, Spennophilus beecheyi . The ground squirrel occurred in large numbers on the post, in association with other known reservoirs and intermediaries of sylvatic plague. Ground squirrel fleas ( Diamanus montanus and Hoplopsyllus anomalus ) were collected from 6 rodent and lagomorph species. Casual species of fleas from the ground squirrel included Malareus telchinum (normally found on Peromyscus and Microtus ) and the nonspecific species Echidnophaga gallinacea and Pulex simulans .

Rearing of Diamanus Montanus (Siphonaptera: Ceratophyllidae) and Hoplopsyllus Anomalus (Siphonaptera: Pulicidae)1

Diamanus montanus and Hoplopsyllus anomalus were reared in plastic jars on a substrate of ground corncobs, using suckling mice as the blood meal source and a mixture of guinea pig diet and blood meal as the larval food. D. montanus was reared at 27°C and 80% RH; H. anomalus was reared at 19°C and 25% RH. Under these conditions, cultures of D. montanus produced a monthly surplus of approximately 150 fleas per jar.

Plague vector studies. 3. The rate deparasitized ground squirrels are reinfested with fleas under field conditions.

A total of 48,996 fleas was collected from 143 ground squirrels. The fleas were in 3 species, Echidnophaga gallinacea, Hoplopsyllus anomalus and Diamanus montanus. When returned to their habitat, most deparasitized animals recovered their normal complement of fleas on or before the third day; and, in most instances, the flea population on the formerly deparasitized squirrels exceeded the normal complement of fleas from the third to the seventh day. Electrical fences were used to confine the ground squirrels.

Plague vector studies. IV. A comparison of insecticide application techniques for flea control on ground squirrels.

An evaluation of the long term residual life of Dieldrin based on the flea index indicated that from the second month through the twelfth month post-treatment the flea index was less than 0.4 fleas per squirrel in 3 of the treated fields, while the control index ranged from 60.5 to 419.5 fleas per host. From the third to the sixth day post-treatment the flea mortality was higher in study areas treated by direct burrow application of Dieldrin (96.3% and 98.0%) than in those study areas where application was by the surface or area method (92.6% and 95.8%). Burrow treatment resulted in a more rapid knockdown of fleas than did surface treatment. These data are based on 89,028 fleas collected from 1423 California Ground Squirrels; the 3 species present of fleas were Diamanus montanus, Hoplopsyllus anomalus , and Echidnophaga gallinacea.

Plague vector studies. I. The rate of transfer of fleas among Citellus, Rattus and Sylvilagus under field conditions in southern California.

The extent of transfer of fleas among Citellus, Rattus and Sylvilagus was studied. Electrical fences were used to confine the mammals in O.4-ha fields. Based on analysis of 92,694 fleas from 620 hosts, it is concluded that Xenopsylla cheopis, Diamanus montanus, and Hoplopsyllus anomalus will attack atypical hosts, in the same habitat as their usual hosts, at epizootiologically significant rates. An X. cheopis index of 1 occurred on ground squirrels (Citellus beecheyi), and of 0.9 on rabbits (Sylvilagus audubonii).

Plague vector studies. II. The role of climatic factors in determining seasonal fluctuations of flea species associated with the California ground squirrel.

Studies were conducted on California ground squirrels confined in O.4-ha electrically-fenced fields to determine the effects of physical factors in the environment on seasonal fluctuations in the population densities of Hoplopsyllus anomalus, Diamanus montanus and Echidnophaga gallinacea. The summer-breeding species, H. anomalus and E. gallinacea, were greatly restricted in their reproductive activities in the experimental field where moisture was supplemented to keep the soil moist to 1 m in depth; the winter-breeding species, D. montanus, was much more reproductively active during the summer in the experimental area where the soil was kept moist. A total of 46,962 fleas was collected from 468 ground squirrels during the course of this study. Trained ferrets were used to pull electrical cables into the ground squirrel burrows to enable the operators to record the relative humidities and temperatures existing at various levels in the burrow systems.