Copepod consumption by amphibians and fish with implications for transmission of Dracunculus species.

Parasitic nematodes in the genus Dracunculus have a complex life cycle that requires more than one host species in both aquatic and terrestrial habitats. The most well-studied species, Dracunculus medinensis, is the causative agent of human Guinea worm disease (dracunculiasis). There are several other Dracunculus species that infect non-human animals, primarily wildlife (reptiles and mammals). The classic route of D. medinensis transmission to humans is through the ingestion of water containing the intermediate host, a cyclopoid copepod, infected with third-stage larvae (L3s). However, many animal hosts (e.g., terrestrial snakes, dogs) of other Dracunculus sp. appear unlikely to ingest a large number of copepods while drinking. Therefore, alternative routes of infection (e.g., paratenic or transport hosts) may facilitate Dracunculus transmission to these species. To better understand the role of paratenic and transport hosts in Dracunculus transmission to animal definitive hosts, we compared copepod ingestion rates for aquatic species (fish, frogs [tadpoles and adults], and newts) which may serve as paratenic or transport hosts. We hypothesized that fish would consume more copepods than amphibians. Our findings confirm that African clawed frogs (Xenopus laevis) and fish consume copepods, but that fish ingest, on average, significantly higher numbers (68% [34/50]) than adult African clawed frogs (36% [18/50]) during a 24-h time period. Our results suggest that amphibians and fish may play a role in the transmission of Dracunculus to definitive hosts. Still, additional research is required to determine whether, in the wild, fish or frogs are serving as paratenic or transport hosts. If so, they may facilitate Dracunculus transmission. However, if these animals simply act as dead-end hosts or as means of copepod population control, they may decrease Dracunculus transmission.

On the potential role of Mergus merganser as transport hosts for Tetracapsuloides bryosalmonae.

Transmission paths in the distribution of proliferative kidney disease (PKD) of salmonids are still largely unknown. In this study, the role of goosander (Mergus merganser) as possible transport host for Tetracapsuloides bryosalmonae through faeces was examined. Goosander fledglings were fed exclusively with diseased brown trout (Salmo trutta fario). In all trout used for feeding, intratubular sporogonic stage of the parasite was confirmed histologically. Between one to 10 hours post-feeding, the goosander faeces were sampled and tested for T. bryosalmonae DNA. In qPCR, only DNA fragments were found, and in conventional PCR, no amplification was confirmed. Therefore, we hypothesize that the role of goosander as transport hosts for T. bryosalmonae via their faeces can be neglected.

The role of the American cockroach (Periplaneta americana) as transport host of Eimeria tenella to chickens.

The role of the American cockroach, Periplaneta americana as transport host for Eimeria tenella was evaluated. Twenty-four cockroaches were orally fed with sporulated oocysts of E. tenella. Their feces and digestive tract were examined for oocysts by sugar centrifugal flotation technique and PCR. Infectivity of the oocysts recovered from the digestive tract of infected cockroaches as well as from their feces was evaluated by orally inoculating them into Boris Brown chickens. E. tenella oocysts were found in the digestive tract and feces of infected cockroaches up to day 4 after ingestion of oocysts. Furthermore, oocysts that were recovered from the digestive tract and feces of cockroaches remained infective for 4 and 3 days after ingestion of oocysts, respectively. Presence of oocysts in the feces of chicken that had been inoculated with either digestive tract or feces of P. americana demonstrated the infectivity of E. tenella oocysts from digestive tract or feces, suggesting that P. americana may play a role in the transmission of E. tenella among chicken and between chicken flocks.

Possible Role of Fish as Transport Hosts for Dracunculus spp. Larvae.

To inform Dracunculus medinensis (Guinea worm) eradication efforts, we evaluated the role of fish as transport hosts for Dracunculus worms. Ferrets fed fish that had ingested infected copepods became infected, highlighting the importance of recommendations to cook fish, bury entrails, and prevent dogs from consuming raw fish and entrails.

Life cycle of Cystoisospora felis (Coccidia: Apicomplexa) in cats and mice.

Cystoisospora felis is a ubiquitous apicomplexan protozoon of cats. The endogenous development of C. felis was studied in cats after feeding them infected mice. For this, five newborn cats were killed at 24, 48, 72, 96, and 120 h after having been fed mesenteric lymph nodes and spleens of mice that were inoculated with C. felis sporulated sporocysts. Asexual and sexual development occurred in enterocytes throughout the villi of the small intestine. The number of asexual generations was not determined with certainty, but there were different sized merozoites. At 24 h, merogony was seen only in the duodenum and the jejunum. Beginning at 48 h, the entire small intestine was parasitized. At 24 h, meronts contained 1-4 zoites, and at 48 h up to 12 zoites. Beginning with 72 h, the ileum was more heavily parasitized than the jejunum. At 96 and 120 h, meronts contained many zoites in various stages of development; some divided by endodyogeny. The multiplication was asynchronous, thus both immature multinucleated meronts and mature merozoites were seen in the same parasitophorous vacuole. Gametogony occurred between 96 and 120 h, and oocysts were present at 120 h. For the study of the development of C. felis in murine tissues, mice were killed from day 1 to 720 d after having been fed 10(5) sporocysts, and their tissues were examined for the parasites microscopically, and by bioassay in cats. The following conclusions were drawn. (1) Cystoisospora felis most frequently invaded the mesenteric lymph nodes of mice and remained there for at least 23 mo. (2) It also invaded the spleen, liver, brain, lung, and skeletal muscle of mice, but division was not seen based on microscopical examination. (3) This species could not be passed from mouse to mouse.

Sarcopromusca pruna (Diptera: Muscidae) as an egg transport host of Dermatobia hominis (Diptera: Cuterebridae) in the cacau region of Bahia, Brazil

Sarcopromusca pruna appears to be the predominant transport host for Dermatobia hominis eggs among cattle herds in central eastern Bahia, Brazil. In the study area, two seasonal peaks of S. Pruna abundance coincide with those of Dermatobia, from mid July through late September and from mid November until early January, two periods of moderate monthly rainfall between anual extremes. Among more than 26,000 flies examined during the study, 75 (all female S. pruna) bore Dermatobia eggs. Certain aspects of Dermatobia behavior and ovoposition habits in the field are also discussed.