A positive relationship between distribution and local abundance is often observed among species in a community. The resource-breadth hypothesis suggests that this pattern is the result of differential abilities among species to utilize available resources, such that generalists are widely distributed and locally abundant, and specialists are narrowly distributed and locally sparse. This hypothesis was tested in a community consisting of 22 species or morphospecies of parasites infecting members of 18 species of fish among 14 sites in 7 small streams in the Appalachian Mountains of North Carolina. A positive relationship between distribution (fraction of sites occupied) and abundance (average local abundance) was evident among parasite species. The number of host species infected by each parasite species was positively related to both distribution and average local abundance; both relationships held after statistical removal of the distribution and abundance of the hosts, respectively. These results support the resource-breadth hypothesis as an explanation for the distribution–abundance relationship in this system.

Seventy-two Mexican garter snakes (Thamnophis eques) and 126 black-bellied garter snakes (T. melanogaster) were collected from 4 localities of the Mesa Central of Mexico between July 1996 and February 1998 and examined for helminths. Both species of garter snakes occurred sympatrically in every locality except in Lake Cuitzeo. Both species of snakes shared 9 helminth species, and in general, T. melanogaster hosted a larger number of species than T. eques. In each locality, a different helminth species showed the highest levels of prevalence and abundance (Spiroxys susanae in Ciénaga de Lerma, Telorchis corti in Lago de Pátzcuaro, Proteocephalus variabilis in Lago de Cuitzeo, and Contracaecum sp. in Lago de Chapala). Helminth communities in garter snakes of the Mesa Central are depauperate and dominated by a single parasite species. In those localities where the snakes occurred in sympatry, helminth communities were, in general, more diverse and species-rich in T. melanogaster. Differences in the ecology and physiology of these species of garter snakes may explain this pattern because black-bellied garter snakes (T. melanogaster) are more aquatic than Mexican garter snakes (T. eques) and primarily eat aquatic prey, potentially exposing themselves to a larger number of helminths transmitted by predator–prey infection. The helminth infracommunities of garter snakes in the Mesa Central of Mexico show a strong Nearctic influence because most of the species infecting these hosts have been recorded in other Nearctic colubrid snakes. However, the helminth infracommunities of these garter snakes are less species-rich and less diverse than those in colubrid snakes in more temperate latitudes. The widespread ecological perturbation of sampling sites in the Mesa Central because of human activity, and geographic differences in foraging ecology of the hosts and, thus, exposure to parasites transmitted by intermediate hosts may help to explain these patterns.

Single species infections with schistosomes, geohelminths, and intestinal protozoans are common over large parts of sub-Saharan Africa, and it is expected that polyparasitism affects a considerable proportion of the population, hence posing a great toll on public health. However, few investigations have been carried out to quantify the extent of polyparasitism. Here, a detailed assessment is reported for the epidemiology of Schistosoma mansoni, geohelminths, and intestinal protozoan infections, with particular emphasis on polyparasitism among 260 community members in rural Côte d'Ivoire. Schistosoma mansoni, Entamoeba coli, and hookworm were the predominant species with prevalences of 71.5, 64.6, and 51.9%, respectively. Only 8 individuals displayed no infection, whereas two-thirds of the population harbored 3 or more parasites concurrently. There were a series of significant pairwise parasite co-occurrences, e.g., between S. mansoni and hookworms and between S. mansoni and E. coli. It is concluded that polyparasitism in the population studied here was very common, which is probably the case also in other areas of rural Côte d'Ivoire and elsewhere in sub-Saharan Africa. These findings call for integrated approaches to effectively control multiple parasitic and protozoan infections.

In 1999, 4 species of cyprinid were surveyed for myxozoan parasites in a watershed in Algonquin Park, Canada; Kathlyn Lake, Broadwing Lake, and Lake Sasajewun were included. Eight species of Myxobolus were found that differed in their prevalence and distribution among the 3 lakes. The oligochaetes and environmental parameters, including sediment types and aquatic plants, of these 3 lakes were surveyed the following year. Oligochaetes belonging to 17 species were collected from the 3 lakes. The distribution patterns of the oligochaete fauna, with respect to the environmental variables, were examined using canonical correspondence analysis. Naidids were predominant in all 3 lakes, particularly in the pebbly and sandy sediment of Lake Sasajewun. The highest percentage of tubificids occurred in the detritus and muddy substrate of Broadwing Lake. These findings indicate that the prevalence of certain oligochaetes is congruent with the absence or presence of particular myxozoan species and that substrates and aquatic plants influence the distribution of certain oligochaete species.

Twenty eyes from 10 Pacific sleeper sharks Somniosus pacificus, infected with the copepod Ommatokoita elongata, were collected in Prince William Sound, Alaska, and the eyes of an additional 18 S. pacificus captured in the same area were inspected for copepods. Prevalence of infection by adult female O. elongata was 97% (n = 28); mean intensity of infection was 1.89 (±1SD = 0.32) adult female copepods per infected shark and 1.0 (±1SD = 0.0) adult female copepods per infected eye. Five of the 20 collected eyes were infected by O. elongata chalimi, and 9 of 20 eyes had 1 to several remnants of bullae embedded in the cornea. Bullae were each associated with a corneal opacity, and anchoring plugs of chalimi were associated with pinpoint lesions in the cornea or conjunctiva. All eyes exhibited marked edema and erosion of the bulbar conjunctiva, and this torus-shaped lesion corresponded to each O. elongata adult female's presumed feeding and abrasion radius. Histological examinations revealed lesions in the anterior segment of eyes to be generally similar, but graded, in severity, and in all eyes they involved the conjunctiva, cornea, filtration angle, and iris. Epithelial lesions were characterized by corneal ulceration, dysplasia, hyperplasia, and heterophilic keratitis, and by ulcerative conjunctivitis accompanied by epithelial hyperplasia with rete peg formation. Disorganization of fibers, necrosis, mineralization, minimal heterophilic influx, and perilimbic neovascularization were associated with bullae in the corneal stroma. Within the limbus there was diffuse histiocytic and lymphocytic inflammation and marked lymphofollicular hyperplasia. Heterophilic and mononuclear anterior uveitis affecting the filtration angle and anterior surface of the iris was also observed in most eyes. One eye had a partial transcorneal prolapse of a ruptured lens, with degenerative changes in the ruptured lens and severe keratitis associated with the anchoring devices of an adult copepod and several chalimi. Fourteen eyes exhibited 1 to several, randomly distributed, small, round to irregular, corneal opacities or pits that were not associated with copepods, and it is likely that these opacities represented lesions associated with adult female or larval anchoring devices from past infections. The avascular cornea represents a niche that is somewhat shielded from host immune reactions, and this, and the fact that the general body surface of sleeper sharks is covered by tall and sharp placoid scales, may partially explain the corneal attachment of O. elongata adult females. It was concluded that O. elongata infections can lead to severe vision impairment in Pacific sleeper sharks but that these infections do not significantly debilitate hosts because they probably do not need to rely on acute vision for their survival.

Several experiments were designed to elucidate the modes of transmission of the myxozoan parasite Enteromyxum scophthalmi to turbot Scophthalmus maximus. Direct transmission of the infections was achieved by cohabitation of infected and test fish, through waterborne contamination from the effluent of a tank containing infected fish, and via the oral route using parasite-infected intestines. The transmission of the turbot enteromyxosis was successful in all the fish exposed to the parasite by the 3 routes; accumulated mortality reached 100% at the end of most experiments. The progress of the infections was monitored by study of the histopathology. Influence of the mode of exposure was observed, with the oral route the fastest to initiate the parasite infections. The temperature also affected the course of the infections, which were established earlier at higher water temperature. Direct fish-to-fish transmission of the disease explains the rapid spreading of the turbot enteromyxosis in farms.

The infective behavior of a mutant Trypanosoma cruzi clone, carrying a targeted deletion of the gp72 gene, was studied in the insect vector Triatoma infestans and in mice. After feeding T. infestans with complement-resistant forms (CRF) of Ynull and wild-type clones, it was observed that the number of parasites released in the bug's feces was reduced to less than 1% in the mutant clone. Both gp72-null and wild-type clones had a low infectivity for mice in comparison with other T. cruzi isolates, probably as a consequence of prolonged in vitro culture. Therefore, the behavior of both clones was tested in highly susceptible BALB suckling mice and immunodeficient athymic mice. After infecting the animals with 10⁵ CRF, wild-type parasites could be detected in fresh blood mounts of most mice, but mutants were never found by this method. However, in 4 of 22 hemocultures from 11 athymic mice, gp72-null epimastigotes carrying the mutant phenotype were reisolated by day 29 of infection. Serological and polymerase chain reaction determinations performed on the blood of animals inoculated with the mutants indicated the possibility of temporary infections, which were extinguished after 90 days. The intact GP72 gene seems essential for sustaining latent infections in immunocompetent animals.

The gametocyte sex ratio of Plasmodium mexicanum, a malaria parasite of western fence lizards, was studied in a modified garden experiment. Each of 6 naturally infected lizards was used to initiate 20 replicate-infections in naive western fence lizards. A significant donor effect was observed for the sex ratios of recipient infections at their maximal parasitemia, and this effect was associated with the sex ratio of the donor infection. In 20 infections in which sex ratio was followed during the course of the infection, 9 revealed constant sex ratios and 11 showed an increase in proportion of males over time. Recipient sex ratio was correlated with another life-history trait, a composite of rate of asexual replication and peak parasitemia, such that higher Rate–Peak scores were associated with infections with less female-biased sex ratios. These results are placed into the context of sex ratio theory that concludes that the degree of selfing of parasite genotypes (number of parasite clones) within the vector will influence the evolution of gametocyte sex ratio. The theory predicts that the sex ratio should be under some genetic control and thus be heritable as observed in the experiment. Clonal diversity should also influence the life-history trait, Rate–Peak, which was found to be correlated with sex ratio.

A 7-kDa protein was purified from extracts of adult Clonorchis sinensis by a combination of ammonium sulfate precipitation, anion exchange chromatography, cation exchange chromatography, gel-filtration chromatography, and reversed-phase FPLC. The 7-kDa protein exists in the excretory–secretory products of adult C. sinensis, but not in extracts of adult Paragonimus westermani. Also, the 7-kDa protein reacted with the sera of patients with clonorchiasis but not with paragonimiasis or normal human sera. To observe the localization of the 7-kDa protein in the tissue of adult C. sinensis, an immunogold labeling method was followed using anti-7-kDa antibody. The gold particles were observed in the basal layer below the tegumental syncytium, in the interstitial matrix of the parenchyma, and in the content of the uterus. The 7-kDa cDNA was obtained through reverse transcription-polymerase chain reaction using a primer designed from N-terminal sequence analysis. Rapid amplification of cDNA ends (5′-RACE) was used to obtain the complete protein coding sequence. The sequence encodes a 90-amino acid polypeptide. The deduced amino acid sequence of the 7-kDa protein revealed no homology with proteins of different organisms reported so far. These results suggest that the 7-kDa protein is a fluid antigen and may be valuable as a tool for the immunodiagnosis of clonorchiasis.

Two carbohydrate epitopes were identified by monoclonal antibodies (KCS and E2) and characterized with respect to their immunoreactivity, monosaccharide structure, and location. Immunofluorescence demonstrated the presence of both epitopes on the surfaces of sporocysts, cercariae, and miracidia of Schistosoma mansoni, Schistosoma haematobium, and Schistosoma japonicum. However, spatial distribution and density of expression varied among species and developmental stages, and neither epitope was detectable on adult worm surfaces. Both glycans were found in the hemolymph of infected, but not uninfected, intermediate snail hosts. The presence of epitopes in hemolymph, as well as in schistosome eggs, is species-specific for KCS, recognizing only S. mansoni, and partly specific for E2, which reacted predominantly with S. haematobium. Immunoaffinity purification of target antigens for KCS and E2 from hemolymph of infected Biomphalaria and Bulinus, respectively, followed by carbohydrate composition analysis revealed a high content of fucose in both glycans. Methylation analysis demonstrated exclusively terminal fucose for the target antigen of KCS and terminal as well as internal fucose for the one of E2. Removal of terminal fucose abolished reactivity with both monoclonal antibodies. Both glycans are different from previously characterized schistosome carbohydrates. Their biological function(s) remain to be defined.

The susceptibility of budgerigars (Melopsittacus undulatus) to graded doses of Toxoplasma gondii oocysts was studied. Sixteen budgerigars were divided into 4 groups (A–D) of 4 each. Birds in groups A–C were fed 100,000, 1,000, or 100 infective oocysts of the VEG strain of T. gondii, respectively. Budgerigars in group D were not fed oocysts and served as controls. All 4 birds in group A died (or were killed) because of acute severe enteritis 5 or 6 days after feeding oocysts (DAFO). Three of the 4 birds in group B were killed (or died) because of toxoplasmosis 9 or 14 DAFO. One budgerigar in group C and the 4 budgerigars in group D remained healthy and were killed 35 or 39 DAFO. Toxoplasma gondii was demonstrated in tissues of all budgerigars fed oocysts. The control budgerigars remained clinically normal and showed no evidence of T. gondii exposure. These results indicate that, compared to other passerines, budgerigars are relatively resistant to clinical toxoplasmosis.

We examine the dynamics of parasitemia and gametocytemia reflected in the preintervention charts of 221 malaria-naive U.S. neurosyphilis patients infected with the St. Elizabeth strain of Plasmodium vivax, for malariatherapy, focusing on the 109 charts for which 15 or more days of patency preceded intervention and daily records encompassed an average 98% of the duration of each infection. Our approximations of merogony cycles (via “local peaks” in parasitemia) seldom fit patterns that correspond to “textbook” tertian brood structures. Peak parasitemia was higher in trophozoite-induced infections than in sporozoite-induced ones. Relative densities of male and female gametocytes appeared to alternate, though without a discernably regular period. Successful transmission to mosquitoes did not depend on detectable gametocytemia or on absence of fever. When gametocytes were detected, transmission success depended on densities of only male gametocytes. Successful feeds occurred on average 4.7 days later in an infection than did failures. Parasitemia was lower in homologous reinfection, gametocytemia lower or absent.

Vertical transmission of larvae is a major pathway in the life cycle of several species of Strongyloides, but evidence for it occurring in humans or dogs with Strongyloides stercoralis is absent. In an effort to determine if vertical transmission could occur with S. stercoralis, each of 3 female dogs was infected with filariform larvae at a different stage of the reproductive cycle, i.e., preconception, gestation, or postpartum. Results showed that none of 6 pups born to a female infected before conception or any of 6 pups born to another female infected during gestation harbored any stage of S. stercoralis when necropsied at parturition. Conversely, all 5 pups that nursed from the female infected immediately postpartum became infected with adult S. stercoralis in their small intestines (range, 56–129 adult worms). Significantly, live filariform larvae of S. stercoralis were observed on 2 different occasions from milk samples taken from the lactating female. Because arrested development of larvae is not known in S. stercoralis, there is no reservoir of larvae in the parenteral tissues of females to queue for passage to the pups and, thus, it is not surprising that only timely infections, perhaps very late in gestation and during lactation, can be successful. These data support previous work in dogs with S. stercoralis, which concluded that vertical transmission through prenatal pathways does not occur, but they are the first from the dog to indicate that vertical transmission of this parasite through transmammary routes is possible. Whether transmammary transmission of S. stercoralis occurs in humans remains unknown but given its immense pathological potential, it should not be overlooked.

Weanling C3H/HeN mice were fed either a torula yeast-based diet deficient in selenium (Se) or the same diet supplemented with 0.2 ppm Se as sodium selenite. After 4 wk of feeding, the mice were inoculated intraperitoneally with the CA-I strain (clone K98) of Trypanosoma cruzi (TC). Before inoculation, mean serum Se levels were 430 versus 61 ng/ml in adequate and deficient mice, respectively. During the ascending phase of parasitemia, the Se-deficient mice exhibited significantly higher levels of parasites at 22–34 days postinfection (PI). However, no difference was found in the subsequent descending phase. As judged by visual examination at 2-mo-PI, some Se-deficient infected mice presented clinical signs of motor dysfunction. At 3-mo-PI, the end of the observation period, this chronic disease developed into a hind limb flaccid paralysis affecting 5 of 8 infected deficient mice. No signs of paralysis were seen in noninfected mice fed either diet or in infected mice fed the Se-adequate diet. At the histological level, both Se-adequate and Se-deficient infected mice showed mild myocarditis and moderate to severe myositis, with increasing intensity from 1- to 3-mo-PI in both groups. However, the severity of myositis was always more intense in the Se-deficient mice so that prominent areas of skeletal muscle replaced by fibrotic tissue were frequently observed. Thus, it can be concluded that Se deficiency in the murine host increases the severity of TC-induced myositis.

Between January and March 2001, eight 4- to 8-wk-old camels (Camelus dromedarius) from 2 farms from Dubai area of the United Arab Emirates were submitted for necropsy examination. The camels had diarrhea of 2–5 days duration. Grossly, a severe diphtheroid-to-hemorrhagic colitis was seen in all animals. Gamonts, unsporulated oocysts, sporulating oocysts, and fully sporulated oocysts were present in the intestinal epithelium and the lamina propria. Fully sporulated oocysts contained 2 sporocysts and 4 sporozoites in each sporocyst. Oocysts from fecal samples resembled oocysts of Isospora orlovi. This is the first report of an isosporan parasite associated with hemorrhagic enteritis in the large intestine of any animal.

Paradollfusnema telfordi n. sp. (Nematoda: Cosmocercidae) from the large intestine of a worm lizard, Rhineura floridana, collected in Florida is described and illustrated. Paradollfusnema telfordi n. sp. represents the second species assigned to the genus and is distinguished from the other species on the basis of caudal papillae patterns in the male: P. telfordi n. sp. with 8 pairs of precloacal papillae, second pair from anterior much larger than others; Paradollfusnema amphisbaenia with 4 or 5 pairs of precloacal papillae, all of equal size.

The nonadult stages, egg strings, eggs, larvae, and cysts of Gordius robustus, Paragordius varius, and Chordodes morgani are described morphometrically. The goal was to document the differences between species and to evaluate the usefulness of morphometrics in species identification. In concert, multivariate analysis of variance (MANOVA) and univariate analysis of variance (ANOVA, a posteriori contrasts) statistical tests demonstrated that each species is morphometrically distinguishable from all others. Additionally, discriminant function analysis indicated that postseptum length, pseudointestine length, and stylet width were the most important variables in the discrimination of species based on larval characters. Finally, differences in oviposition behaviors among these 3 species were found. It is suggested that ovipositioning differences may place larvae into distinct niches and may ultimately lead to the use of different paratenic hosts by different gordiid species.

Two new species of lepocreadiid trematodes are reported from marine fishes from the Taiwan Straits, China: Diploproctodaeum spinosus n. sp. from the intestine of Takifugu oblongus (= Fugu oblongus) and Preptetos parapristipomae n. sp. from Parapristipoma trilineatum. Diploproctodaeum spinosus differs from the known species of Diploproctodaeum, with 1 spine at the base of the ejaculatory duct. Preptetos parapristipomae is most similar to Preptetos rotto in having an entire ovary but differs from it in the sucker ratio, distribution of the uterus, position of the cirrus sac, and locality.

Phylogenetic relationships within the kinetoplastid flagellates were inferred from comparisons of small-subunit ribosomal RNA gene sequences. These included 5 new gene sequences, Trypanosoma fallisi (2,239 bp), Trypanosoma chattoni (2,180 bp), Trypanosoma mega (2,211 bp), Trypanosoma neveulemairei (2,197 bp), and Trypanosoma ranarum (2,203 bp). Trees produced using maximum-parsimony and distance-matrix methods (least-squares, neighbor-joining, and maximum-likelihood), supported by strong bootstrap and quartet-puzzle analyses, indicated that the trypanosomes are a monophyletic group that divides into 2 major lineages, the salivarian trypanosomes and the nonsalivarian trypanosomes. The nonsalivarian trypanosomes further divide into 2 lineages, 1 containing trypanosomes of birds, mammals, and reptiles and the other containing trypanosomes of fish, reptiles, and anurans. Among the giant trypanosomes, T. chattoni is clearly shown to be distantly related to all the other anuran trypanosome species. Trypanosoma mega is closely associated with T. fallisi and T. ranarum, whereas T. neveulemairei and Trypanosoma rotatorium are sister taxa. The branching order of the anuran trypanosomes suggests that some toad trypanosomes may have evolved by host switching from frogs to toads.

During a parasitological examination of 45 specimens of Acanthisthius brasilianus (Valenciennes, 1828) Jordan et Eigenmann, 1890, from waters off Mar del Plata, Argentina (38°08′S, 57°32′W), several specimens of cucullanid nematodes were collected from the intestines. A new species, Dichelyne (Cucullanellus) szidati n. sp., is described (prevalence 42.2%, mean intensity 2.7). The new species differs from its congeners inhabiting the southwestern Atlantic by the distribution pattern of caudal papillae, particularly the ninth pair, length of the body and spicules, and the position of the intestinal cecum (ventral), the excretory pore (posterior to esophagus), and the deirids (at the level of esophageal posterior end).

A new species of Leucocytozoon with gametocytes in fusiform host cells is described from the Bukharan great tit Parus bokharensis. It represents the first leucocytozoid in which the host cell nucleus is split into 2 more or less symmetrical portions, each located at an end of the host cell within its elongated fusiform processes. This species appears to be restricted with respect to geography and host.

Epimastigote culture forms of different isolates of Trypanosoma cruzi from different mammal hosts, humans, and vectors were tested with FITC-conjugated peanut agglutinin lectin (PNA–FITC). The parasites maintained in axenic medium, liver infusion tryptose, were evaluated by flow cytometric analyses; whereas T. cruzi I (TcI), which is associated with the sylvatic transmission cycle, was labeled in high percentages with PNA (88–99.2%), T. cruzi II (TcII) (parasites associated with domiciliar cycle) and T. cruzi, zymodeme 3 (Tc/Z3) (also associated with the sylvatic cycle) were labeled in low percentages (TcII, 0–26% and Tc/Z3, 0–12.6%). It was demonstrated that it is possible to differentiate the 2 main T. cruzi subpopulations, TcI and TcII, using Arachis hypogaea. These results also showed a higher variability in TcII in terms of PNA binding.

Red deer (Cervus elaphus elaphus) were infected experimentally with Parelaphostrongylus tenuis in New Brunswick, Canada, and with Elaphostrongylus cervi in New Zealand. Excretory–secretory (E–S) antigens from adult P. tenuis were evaluated for their serodiagnostic potential in identifying P. tenuis and heterologous E. cervi infections in a Western blot. The antigen recognition profile of sera from animals infected with P. tenuis varied between individuals and with duration of infections, whereas that of pooled sera from animals infected with E. cervi showed less variation. A single molecule of 42–43 kDa was recognized consistently by sera from all animals infected with either P. tenuis or E. cervi. Sera from unexposed control deer and from those with other heterologous nematode infections did not consistently identify this antigen. Serorecognition of the 42–43-kDa antigen by deer infected with P. tenuis resulted in a sensitivity of 99% and a specificity of 85% (≥1 mo postinfection). Although antibody to this antigen waned with time, the persistence of recognition up to 34 mo postinfection with P. tenuis exemplifies its diagnostic value. The sensitivity and specificity of diagnosis using this molecule were each 100% for identifying deer infected with E. cervi (≥3 mo postinfection). Two other molecules from E–S of adult P. tenuis, 26–28 and 10–12 kDa, were also diagnostic, although their recognition was not persistent throughout infections. These 2 molecules may prove useful in combination with the 42–43-kDa antigen to help identify all infected animals during all phases of infections. This research represents the first conclusive identification of antigens with real potential for reliable antemortem immunodiagnosis of both P. tenuis infections and heterologous E. cervi infections.

An indirect fluorescent antibody test (IFAT) for detection of Toxoplasma gondii infection was validated using serum from 77 necropsied southern sea otters (Enhydra lutris nereis) whose T. gondii infection status was determined through immunohistochemistry and parasite isolation in cell culture. Twenty-eight otters (36%) were positive for T. gondii by immunohistochemistry or parasite isolation or both, whereas 49 (64%) were negative by both tests. At a cutoff of 1:320, combined values for IFAT sensitivity and specificity were maximized at 96.4 and 67.3%, respectively. The area under the receiver-operating characteristic curve for the IFAT was 0.84. A titer of 1:320 was used as cutoff when screening serum collected from live-sampled sea otters from California (n = 80), Washington (n = 21), and Alaska (n = 65) for T. gondii infection. Thirty-six percent (29 out of 80) of California sea otters (E. lutris nereis) and 38% (8 out of 21) of Washington sea otters (E. lutris kenyoni) were seropositive for T. gondii, compared with 0% (0 out of 65) of Alaskan sea otters (E. lutris kenyoni).

Tubulin ligands known to be toxic to certain organisms or cells were tested for their ability to inhibit proliferation of trypanosomes in culture. Tubulin was purified from Trypanosoma brucei brucei or rat brain by poly-l-lysine affinity chromatography and used in binding studies in order to compare the binding of [³H]mebendazole to trypanosome and mammalian tubulin. All the compounds tested in culture inhibited trypanosome proliferation in a concentration-dependent manner. The concentration required to inhibit trypanosome proliferation by 50 or 90% (IC₅₀ or IC₉₀) in 24 hr was determined for each compound. There were no significant differences (P > 0.05) among the benzimidazoles (BZs), but colchicine and vinblastine caused significantly greater inhibitions than the BZs (P < 0.02 and P < 0.005, respectively). Increasing the incubation time to 72 hr caused a 2- to 4-fold lowering of the IC₅₀ and IC₉₀ values for all the drugs. In the binding assays, there was higher total binding of [³H]mebendazole to trypanosome than rat brain tubulin. The results suggest that the inhibition of trypanosome growth was caused by the specific interaction of these ligands with trypanosome tubulin. Trypanosome tubulin is, therefore, a reasonable target against which novel drugs can be developed to control trypanosomiasis.

Recent studies have suggested that intracellular Wolbachia spp. endobacteria are necessary for the reproduction and survival of filarial nematodes. The effects of antibiotics that are active against related bacteria on adult worms and microfilariae (Mf) of Brugia malayi in vitro were investigated. Antibiotics tested were doxycycline (Doxy), tetracycline (Tet), rifampicin (Rif), azithromycin (Azith), and chloramphenicol (Chlor). Doxy, Tet, Rif, and Azith reduced release of Mf by adult female worms. The minimum effective concentrations that reduced Mf release by 50% were 5 μg/ml for Doxy, 20 μg/ml for Tet, 40 μg/ml for Rif, and 100 μg/ml for Azith. The same drugs (at higher concentrations) killed adult worms and Mf. Embryograms showed that Tets blocked embryogenesis in female worms. Electron microscopy (EM) showed that the Tets, Rif, and Azith cleared Wolbachia spp. from adult worms and damaged developing embryos. These studies show that antibiotics active against Rickettsiaceae affect adult B. malayi worms and Mf in vitro. Additional studies will be needed to elucidate the mechanisms of action of these antibiotics on Wolbachia and filarial worms.

Membrane transporter P-glycoproteins (Pgps) are present in a number of nematode species, including Haemonchus contortus. Allelic variation in some Pgp genes has been found to be associated with resistance to the anthelmintic ivermectin (IVM), although functional verification of a role for Pgps in IVM resistance has yet to be demonstrated. By in situ hybridization, the distribution of Pgp mRNA was visualized in transverse cryosections of adult H. contortus, using a digoxigenin-labeled cDNA probe encoding the ATP-binding region of an H. contortus Pgp. The probe sequence targeted a conserved ATP-binding region of Pgp-A (97.9% identity). It also shared 49.7–71.1% identity with 11 other Pgp sequences previously identified in H. contortus and may hybridize these sequences to give an overall measure of the total P-glycoprotein mRNA. Staining was predominately localized along the intestinal tract of the worms, with the most intense staining localized in the pharynx and anterior intestine. In the mid- and posterior intestinal regions, staining was restricted to the luminal side of the intestine. Some staining was also associated with the vas deferens and the lateral hypodermal chords anterior to the nerve ring. Using densitometry, the levels of Pgp mRNA in the pharynges of unselected and IVM- and moxidectin (MOX)-selected strains of male and female H. contortus were compared. No differences were detected between the levels of expression of Pgp in the susceptible strain versus the IVM- or MOX-selected strains. Evidence in the literature suggests that not all Pgp homologues are linked to chemical resistance phenotypes. It is thus possible that expression of 1 of the H. contortus Pgps is altered in IVM-resistant strains but that this phenomenon was undetectable in our experiments.

Resistance of Acanthamoeba castellanii cysts to disinfection agents, antimicrobial agents, heat, freeze–thawing, ultraviolet radiation (UV), γ irradiation, and cellulase were evaluated in vitro. Following exposure to different agents, the cysts were removed and cultured for A. castellanii trophozoites for 3–14 days. Solutions containing 20% isopropyl alcohol or 10% formalin effectively killed A. castellanii cysts. Hydrogen peroxide (3%, AOSept Disinfectant) effectively killed A. castellanii cysts after 4 hr of exposure. Polyhexamethylene biguanide (0.02%), clotrimazole (0.1%), or propamidine isethionate (Brolene) were effective in killing A. castellanii cysts in vitro. Acanthamoeba castellanii cysts were resistant to both 250 K rads of γ irradiation and 800 mJ/cm² of UV irradiation. Excystment of trophozoites was accelerated after exposure to 10, 100, and, 1,000 units of cellulase. These results suggest that A. castellanii cysts benefit by enhanced survival because of their resistance to very harsh environmental conditions.

Sarcocysts of Sarcocystis greineri in the Virginia opossum (Didelphis virginiana) were observed for documenting sarcocyst prevalence, seasonal prevalence, and muscle specificity. Characteristics of sarcocysts found in striated muscle were recorded, as were light microscopy measurements. Overall prevalence of sarcocysts in striated muscle was 10.0% (24/240). No statistical difference (P = 0.156) in prevalence was detected between summer (13.1%; 16/122) and fall (6.7%; 8/118). Sarcocysts were found in muscles of the diaphragm, leg, breast, tongue, back, and esophagus. Diaphragm had the highest specificity of 72.7% (8/11), which was significantly different (P = 0.05) when compared with tongue and esophagus at 16.6% (1/6). Breast and leg muscle had a specificity of sarcocysts of 54.5% (6/11), whereas 27.2% (3/11) of back muscles contained sarcocysts.

The digenetic trematode Cotylotretus grandis is redescribed on the basis of 130 specimens recovered from the body cavity and small intestine of 5 roseate spoonbills Ajaia ajaja (Aves, Ciconiiformes, Threskiornithidae) captured in the Pantanal do Mato Grosso, Brazil. The spoonbill A. ajaja is the only host recorded for specimens of C. grandis since 1819, when the species was proposed by Rudolphi as Distoma grande. The synonymy of Mesaulus Braun, 1902, with Cotylotretus Odhner, 1902, is discussed and confirmed after morphological analysis of the specimens.

Stictodora lari Yamaguti, 1939 (Digenea: Heterophyidae) was originally reported as an avian intestinal parasite and is here reported in humans. The patients were adults, aged 46–69 (2 men and 4 women), who resided in coastal villages in Sachon-gun, Kyongsangnam-do, or Shinan-gun, Chollanam-do, in the Republic of Korea. The worms were recovered after praziquantel treatment and purgation with magnesium salts. A total of 15 S. lari specimens (1–10 per individual) was collected, together with 5 other species of intestinal flukes. The flukes were morphologically characterized by a small body size (0.70–0.86 mm long and 0.27–0.36 mm wide), a ventrogenital sac, and a gonotyl armed with 70–80 spines in the form of a comma or reversed comma lying along their lateral margin. The patients had eaten the raw flesh of mullets and gobies that had been caught in an estuary near their villages. To the best of our knowledge, this is the first record of a human S. lari infection.

Sections of muscle from Florida black bears (Ursus americanus floridanus) collected in the state of Florida were observed for the presence of Sarcocystis sp. sarcocysts. Two of 132 (1.5%) black bears had muscle sections containing sarcocysts. One sarcocyst was observed per muscle section. The sarcocysts averaged 181.5 × 99.0 μm by light microscopy of hematoxylin and eosin-stained sections.

Three species of freshwater pulmonate snails of Lymnaeidae have been reported from Korea, Radix auricularia coreana, Austropeplea ollula, and Fossaria truncatula. Of these 3 species, only A. ollula was naturally infected with Neodiplostomum seoulense cercariae (prevalence, 0.3%). In experiments with the laboratory-reared snails, A. ollula was found to be susceptible to the N. seoulense miracidia (prevalence, 10%). This is the first report of A. ollula as the first molluscan intermediate host for N. seoulense in Korea.

Morphological identification of tapeworm species at larval stages (procercoids and cysticercoids) is often difficult because few diagnostic characters are available. In the present study, a molecular approach (sequencing of partial 18S rDNA gene) was used to evaluate the genetic similarity between adult specimens of Cyathocephalus truncatus (Pallas, 1871) (Cestoda: Spathebothriidea) found in fish, its definitive host, and procercoids of the same species recovered from amphipod, Echinogammarus stammeri (Karaman, 1931). Furthermore, cestode cysticercoids of uncertain species were found in the amphipod's hemocoel. The sequences obtained from adults and procercoids were identical, and even very similar to those of C. truncatus available in GenBank, whereas the sequences obtained from cysticercoids differed significantly from those of adults and procercoids, indicating that these larvae belong to another species; later it was demonstrated that they were cysticercoids of Microsomacanthus pachycephala (Linstow, 1972), a cestode of the Hymenolepididae (Cyclophyllidea). The results of this investigation show that the comparison of nucleotide sequence data may avoid misclassification of developmental stages of parasites, which use the same intermediate host.

Intestinal coccidiosis was diagnosed histologically in the small intestine of a spinner dolphin (Stenella longirostris). Numerous intralesional coccidia were present in mucosal epithelial cells. Schizonts, gamonts, and unsporulated oocysts were seen. Schizonts were up to 30 × 20 μm and contained up to 16 merozoites, which measured 10–12 × 2 μm. Unsporulated oocysts were about 9–12 × 8–10 μm. This is the first report of intestinal coccidiosis in a spinner dolphin.

Acute toxoplasmosis was diagnosed in 2 captive dik-dik (Madoqua guentheri smithi) in the Houston Zoo. Both animals became ill suddenly and died in spite of supportive therapy. Toxoplasma gondii was identified in tissues of both animals immunohistochemically, and antibodies to T. gondii were found in titers of 1:800 or more in both animals upon examination by the modified agglutination test. The cause of death was considered to be toxoplasmic pneumonia. This is the first report of toxoplasmosis in M. g. smithi.

Cryptosporidium parvum oocysts were stored in 1-ml aliquots of filtered river water at −20, 4, 10, and 21–23 C in the dark. Oocysts were also added to filter-sterilized river water samples and stored at 21–23 C. The infectivity of oocysts stored under different conditions was assayed at weekly intervals through infection of human adenocarcinoma ileocecal (HCT-8) cell monolayers. Wells containing between 10 and 100 foci of infection were enumerated by immunofluorescent microscopy, and the number of infective oocysts was calculated. No infectious oocysts were detected after 1 wk at −20 C. The number of infective oocysts stored at 4 C decreased 5-fold, and the number of those stored at 10 C decreased 2.5-fold after 14 wk. The infectivity of oocysts stored in potassium dichromate (positive control) at 4 C decreased 2-fold over 14 wk. The number of infective oocysts in filter-sterilized and non–filter-sterilized river water stored at 21–23 C decreased by 3.3 and 2.6 log units, respectively, over 12 wk, and no foci of infection were detected at 14 wk. The results show that as temperature increased from 4 to 23 C, the duration of oocyst infectivity decreased.