Oscar J. Pung

Trypanosoma cruzi in wild raccoons, opossums, and triatomine bugs in southeast Georgia, U.S.A.

The prevalence of Trypanosoma cruzi infection among wild opossums and raccoons live-trapped in 6 southeast Georgia counties was determined. Epimastigotes typical of T. cruzi were observed in liver infusion tryptose medium cultures of blood from 6 of 39 opossums (15.4%) and 12 of 54 raccoons (22.2%). Trypomastigotes (6,000/ml) were observed in a wet mount of blood from 1 of the animals, a raccoon trapped on St. Catherines Island in Liberty County. In addition, T. cruzi parasites were observed in the gut contents of 3 of 5 specimens of the triatomine bug Triatoma sanguisuga (Leconte) collected near human dwellings in Bulloch County. This is the first report of T. cruzi-infected triatomine bugs in Georgia.

EFFECTS OF MICROPHALLUS TURGIDUS (TREMATODA: MICROPHALLIDAE) ON THE PREDATION, BEHAVIOR, AND SWIMMING STAMINA OF THE GRASS SHRIMP PALAEMONETES PUGIO

The effect of the trematode Microphallus turgidus on its second intermediate host, the grass shrimp, Palaemonetes pugio, was tested. To do so, we measured the susceptibility of infected and uninfected shrimp to predation by the mummichog, Fundulus heteroclitus. Shrimp behavior was compared in the presence and absence of a fish predator, and the swimming stamina and backthrust escape responses of infected and uninfected shrimp were measured. Infected shrimp were more likely to be eaten by a predator than uninfected shrimp, had lower swimming stamina, and spent more time swimming and less time motionless in the presence of a predator. There was no difference between backthrust distances traveled in response to a stimulus by either infected or uninfected shrimp. Thus, M. turgidus may increase the predation of P. pugio in the wild, possibly by affecting the swimming stamina and predator avoidance responses of the shrimp.

Prevalence of Antibodies to Trypanosoma cruzi in Raccoons (Procyon lotor) From an Urban Area of Northern Virginia

Raccoons (Procyon lotor) are reservoir hosts for Trypanosoma cruzi. A 3-yr-long serological survey was conducted to determine the prevalence of antibodies to this zoonotic parasite in raccoons collected from Fairfax County, Virginia, a suburban/urban area outside Washington, D.C. Serum samples from 464 raccoons were examined for T. cruzi antibodies at a 1:40 dilution with an indirect fluorescent antibody test (IFAT) and Brazil strain T. cruzi amastigotes and trypomastigotes as antigen. A positive IFAT test was found in 154 (33%) of the 464 samples. The yearly prevalence was 49 of 132 (37%) in 2000; 19 of 120 (16%) in 2001; and 86 of 212 (41%) in 2002. Our study indicates that raccoons in this area of Virginia are frequently exposed to T. cruzi.

PREVALENCE, GEOGRAPHIC DISTRIBUTION, AND FITNESS EFFECTS OF MICROPHALLUS TURGIDUS (TREMATODA: MICROPHALLIDAE) IN GRASS SHRIMP (PALAEMONETES SPP.) FROM COASTAL GEORGIA

Grass shrimp, Palaemonetes pugio Holthuis and P. vulgaris (Say), were collected at 11 localities along the coast of Georgia and surveyed for digenetic trematode metacercariae. The effect of trematode infection on grass shrimp fitness was also examined. Microphallus turgidus (Leigh) was the only trematode observed. The prevalence of metacercarial cysts of this parasite in P. pugio (75%) was higher than in P. vulgaris (24%), as were the mean intensity, abundance, and population density (no. cysts/cm host body length) of the parasite. Infected shrimp were found at every collection locality and parasite prevalence and density were greatest in P. pugio from higher salinity localities (≥20 parts per thousand [ppt]). There was no relation between host body size and parasite density in P. vulgaris, and parasite density increased with host body size in P. pugio, suggesting that the parasite does not affect host survival. There was no relation between parasite density and shrimp egg mass, but nonovigerous female P. pugio were more heavily infected than ovigerous ones. In addition, 1 metacercaria of M. turgidus in each of 2 specimens of P. vulgaris was parasitized by the haplosporidian Urosporidium crescens De Turk. This represents a new shrimp host record for this hyperparasite.

COMPARISON OF SEROLOGICAL METHODS AND BLOOD CULTURE FOR DETECTION OF TRYPANOSOMA CRUZI INFECTION IN RACCOONS (PROCYON LOTOR)

The indirect immunofluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) were compared with blood culture for the detection of Trypanosoma cruzi infection in 83 raccoons (Procyon lotor) trapped in 4 counties of southeast Georgia. Both IFAT and ELISA detected 24 of 25 culture-positive samples (96% sensitivity). Cultures from 25 raccoons (30%) were positive for epimastigotes, whereas a total of 50 raccoons (60%) was seropositive by either the IFAT or ELISA. Forty-five of 83 serum samples (54%) were positive for anti-T. cruzi antibodies with the ELISA, and 47 were IFAT positive (57%). Forty-two of the 50 seropositive raccoons (84%) were seropositive by both tests. Endpoint titers of IFAT-positive samples were determined by testing doubling dilutions from 1:40 to 1:1280. High titers of 640 and 320 were observed for 4 raccoons trapped in 1 county (St. Catherines Island, Liberty County) and titers of 160 for 1–2 raccoons from each of the 4 counties sampled. IFAT titers and ELISA optical density values were positively correlated. Both serological tests have a high sensitivity and should be excellent tools for studying the prevalence of T. cruzi in wildlife populations.

ECTOPARASITES AND GASTROINTESTINAL HELMINTHS OF SOUTHERN FLYING SQUIRRELS IN SOUTHEAST GEORGIA

Southern flying squirrels (Glaucomys volans) from southeastern Georgia were examined for ectoparasites and gastrointestinal helminths. Ten species of ectoparasites were recovered, including 3 species of sucking lice (Hoplopleura trispinosa, Microphthirus uncinatus, and Neohaematopinus sciuropteri), 1 species of flea (Orchopeas howardi), 2 species of ticks (Amblyomma maculatum and Ixodes scapularis), 3 species of mesostigmatid mites (Androlaelaps casalis, A. fahrenholzi, and Haemogamasus ambulans), and 1 species of chigger (Leptotrombidium peromysci). Only the sucking lice and fleas were common on this host. M. uncinatus is reported for the first time from eastern North America. The 2 most commonly collected ectoparasites, N. sciuropteri (prevalence = 63%) and O. howardi (prevalence = 47%), have previously been shown to be vectors of the rickettsial zoonotic agent that causes sporadic epidemic typhus. Also, 3 nematodes (Citellinema bifurcatum, Strongyloides robustus, and Syphacia thompsoni), 1 unidentified cestode, and 1 acanthocephalan (Moniliformis clarki) were found in flying squirrel gastrointestinal tracts. With the exception of S. thompsoni, which was common and relatively abundant in the cecum (prevalence = 94%, intensity = 51 ± 12), both the prevalence and intensity of helminth parasites were low. The nematode S. thompsoni and the acanthocephalan M. clarki are new state records for tree squirrels in Georgia.

Amplification of Trypanosoma cruzi-specific DNA sequences in formalin-fixed raccoon tissues using polymerase chain reaction.

This investigation applied polymerase chain reaction (PCR) using 3 sets of Trypanosoma cruzi–specific primers to amplify DNA from 31 archived formalin-fixed and fresh-frozen raccoon hearts. PCR successfully amplified T. cruzi–specific sequences, with at least 1 primer set, from multiple sites within the myocardium of formalin-fixed and fresh-frozen raccoon hearts that had previously tested positive using enzyme-linked immunosorbent assay and indirect immunofluorescent antibody titer in the absence of positive hemoculture results. Trypanosoma cruzi DNA was most frequently amplified from the interventricular septum, right ventricle, and left atrium. In addition, T. cruzi DNA was amplified with all 3 primers in at least 1 raccoon that was hemoculture positive and 2 animals that were borderline negative for the T. cruzi antibody and hemoculture negative. The amplification of T. cruzi–specific DNA sequences in the presence of an elevated antibody titer and negative culture results suggests good sensitivity of this method for detecting the presence of the parasite in archival tissues.

IN VITRO CULTIVATION OF MICROPHALLUS TURGIDUS (TREMATODA: MICROPHALLIDAE) FROM METACERCARIA TO OVIGEROUS ADULT WITH CONTINUATION OF THE LIFE CYCLE IN THE LABORATORY

Abstract In vitro cultivation of trematodes would aid studies on the basic biology of the parasites and the development of chemotherapies and vaccines. Our goal was to measure the in vitro survival and maturation of metacercariae of Microphallus turgidus under different culture conditions. Metacercariae of M. turgidus from grass shrimp (Palaemonetes pugio) were excysted and cultured in humidified air at 37 C in RPMI-1640 medium supplemented with 20% calf, chicken, or horse serum. Deposition of eggs was greatest in media containing horse or calf serum. Worms survived longest at 37 C, but did not produce greater numbers of eggs than worms cultured in RPMI-1640–supplemented horse serum at 42 C. Most eggs deposited in vitro (>80%) were normal in shape and, after incubation for 10 days at 30 C in brackish water, approximately 30% of them contained miracidia. Eighteen percent of hydrobiid snails (Spurwinkia salsa) fed these eggs shed cercariae 5–6 wk later. The cercariae were infective to grass shrimp (Palaemonetes vulgaris) and developed into metacercariae. This study is significant because it is the second instance in which a digenean, and the first time that a microphallid, has been demonstrated to develop in vitro from metacercariae into adult worms capable of producing infective eggs.

SURVEY AND HOST FITNESS EFFECTS OF RED-COCKADED WOODPECKER BLOOD PARASITES AND NEST CAVITY ARTHROPODS

Blood parasites and nest cavity arthropods associated with the red-cockaded woodpecker (Picoides borealis) were surveyed and the impact of blood-feeding arthropods on woodpecker fitness traits was assessed. Five woodpeckers (8%) were infected with unidentified microfilariae, and 1 woodpecker (2%) was infected with 2 species of haemoproteid (Haemoproteus velans and Haemoproteus borgesi). This is the first record of haemoproteids in this species and the first observation of H. borgesi in North America. We collected representatives of at least 6 families of mites and 12 families of primarily commensal insects from woodpecker cavities. Only a few specimens of blood-feeding insects were recovered. The mite Androlaelaps casalis was the most common hematophagous arthropod (prevalence = 76%, mean density = 51 ± 7 mites/cavity). The number of A. casalis mites increased with cavity age but there was no association between the number of mites and the number of woodpecker eggs laid or the number of hatchlings or fledglings. In conclusion, the prevalence of blood parasites in the red-cockaded woodpecker is low, woodpecker cavities are not heavily infested with blood-feeding insects, and there is no evidence that A. casalis mites affect woodpecker fitness.

Parasitic and Phoretic Arthropods of the Oldfield Mouse (Peromyscus polionotus) from Burned Habitats with Additional Ectoparasite Records from the Eastern Harvest Mouse (Reithrodontomys humulis) and Southern Short-Tailed Shrew (Blarina carolinensis)

Abstract We recorded 12 species of parasitic or phoretic arthropods from 112 live-trapped oldfield mice (Peromyscus polionotus) in southeastern Georgia, U.S.A.: 1 species of sucking louse (Hoplopleura hesperomydis), 1 flea (Peromyscopsylla scotti*), 1 bot (Cuterebra fontinella*), 2 ticks (Dermacentor variabilis and Ixodes scapularis), 3 mesostigmatid mites (Androlaelaps fahrenholzi, Haemogamasus liponyssoides,* and Haemogamasus longitarsus*), 2 fur mites (Glycyphagus hypudaei, Radfordia subuliger*), and 2 chiggers (Euschoengastia peromysci* and Leptotrombidium peromysci*) including the first records (asterisked names) for 7 species from this host. We recorded 4 species of arthropods, all of them mites, from 1 eastern harvest mouse (Reithrodontomys humulis): A. fahrenholzi, R. subuliger, E. peromysci,* and L. peromysci,* including 2 new records (asterisked) from this host. We also recorded 6 species of mites from 5 southern short-tailed shrews (Blarina carolinensis): the mesostigmatids Echinonyssus blarinae and H. liponyssoides; the fur mites Asiochirus blarina,* Blarinobia simplex,* and Protomyobia blarinae;* and the chigger Comatacarus americanus,* including 4 new Georgia state records (asterisked) from this host.