Regulatory factors and structure of a component population of the spionid Polydora bioccipitalis infesting the surf clam Mesodesma donacium

Spionidae, particularly polydorids, are common polychaete parasites of edible mollusks around the world. However, our understanding of the regulatory factors and population structure of these parasites is scant. In this study involving Polydora bioccipitalis and the surf clam Mesodesma donacium we evaluated (1) the environmental correlates of the prevalence and mean intensity of the infestation, (2) the relationship between the number of egg capsules and juvenile and adult parasites and the time elapsed since infestation, and (3) the spatial patterns of juveniles and adults within the host. Environmental factors showed no significant correlations with prevalence and mean intensity, suggesting that these factors do not act directly as regulators. Rather, storm surges seemingly induced clam stranding, which in turn affected both the prevalence and intensity of the infestation. The numbers of juveniles and egg capsules in blisters were significantly related to the time since infestation, suggesting mechanisms of use and expansion of the space within the host. Juvenile worms showed an aggregated distribution that was probably related to the episodic nature of infestation events, whereas adults exhibited uniform distributions that probably reflect territorial behavior and reproductive strategies.     

Ixodid ticks of impala (Aepyceros melampus) in Swaziland: effect of age class,sex, body condition and management

Five species of ixodid ticks, Amhlyomma hebraeum, Boophilus decoloratus, Rhipicephalus appendiculatus, R. evertsi evertsi and R. muehlensi, were commonly collected from impala (Aepyceros melampus) in the Mlawula-Mbuluzi-Simunye Nature Reserve and Protected Area complex in north-eastern Swaziland. The prevalence and apparent intensity of infestation of most tick species was greater on yearlings (13-24 months of age) and adults (> 24 months) than on lambs (≤12 months), and on adult males than on adult females. The packed cell volume and marrow dry weight were lower in impala infested with A. hebraeum, and in lambs and adults with moderate to heavy loads of R. muehlensi and/or R. appendiculatus. The age and sex patterns of tick infestation were probably determined by both body condition and host behaviour. The prevalence and apparent intensity of infestation of most tick species was greater in the unmanaged, densely populated area of the reserve than in the managed area from which impala had been culled. This trend was consistent in all months, and in all age classes.     

Gill Ectoparasites of Juvenile Rainbow Trout and Brown Trout in the Upper Colorado River

Abstract

During 1996 and 1997, 112 rainbow trout Oncorhynchus mykiss and 204 brown trout Salmo trutta, all young of the year, were sampled from a 40-km study area of the upper Colorado River and were examined for gill parasites. Ambiphrya, Chilodonella, Ichthyobodo, Apiosoma, Trichodina, Trichodinella, Tripartiella, Epistylis, and an unidentified cochliopodid amoeba were the representative protozoan genera observed on fish examined. Significant month–year–species interactions (P = 0.0295) were revealed, reflecting the changes in infestation prevalence among months, years, and species of salmonid. Greater ectoparasite richness was observed in downstream sections of the study area, most notably near Hot Sulphur Springs, Colorado. Peaks of infestation intensity and ectoparasite richness occurred in August and September of both years, presumably because of high mean water temperatures and low flows during that time.     

Abundance of the Parasitic Copepod Caligus elongatus on Wild Pollock near Commercial Salmonid Net-Pens

Abstract

Between July and December 1993, wild pollock Pollachius virens collected near salmonid net-pens on the Atlantic coast of Maine in the United States were examined for parasitic copepods of the family Caligidae to determine the role of pollock as host reservoirs. Only Caligus elongatus was detected on 1,456 pollock sampled. Most pollock (97.39%) had two or fewer sea lice per fish. A maximum prevalence (percent of fish infested) of 50%, an abundance (average number per fish) of 0.9, and an intensity (average number per infested fish) of L79 were recorded. Only one larval C. elongatus was found. No seasonal or geographic trends in infestation statistics were observed.     

An improved drench for the treatment of the tapeworm,Moniezia expansa,in sheep

Extract

The treatment of sheep specifically for tapeworm infestation has generally not been advocated, most authorities maintaining that Moniezia expansa is rarely pathogenic when not associated with concurrent nematode infestations. Most sheep develop a good immunity to these parasites which are usually expelled within three months of the host contracting the infestation. On the other hand, there are numerous scattered references to loss of condition and occasionally to deaths attributed to Moniezia infestation in lambs.     

Prevalence,pathology and risk factors for coccidiosis in domestic rabbits (Oryctolagus cuniculus) in selected regions in Kenya

Background: The potential for rabbit production in Kenya is high. However, high morbidity and mortality of domestic rabbits were reported.

Objective: The aim of the study was to determine the pathology, prevalence and the predisposing factors to coccidiosis in domestic rabbits in selected regions in Kenya.

Animals and methods: A total of 61 farms keeping rabbits in six different counties were visited in the survey. A total of 2680 live rabbits were examined and 61 rabbits and 302 fecal samples were randomly collected from the farms and examined for coccidian oocysts by ante-mortem and post-mortem methods. The predisposing factors to coccidiosis were assessed through questionnaires and direct observation. Chi square (χ²) statistics was used with P values < 0.05 considered statistically significant.

Results: Of the 302 fecal samples, 85% (P < 0.001) contained coccidian oocysts and 2% harbored nematode eggs (Passalurus ambiguous). The overall prevalence of Eimeria spp. infestation was 85.1% in the study area and 90.2% in the individual rabbits, while prevalence of intestinal coccidiosis and hepatic coccidiosis was 29.5% and 11.5%, respectively. Higher counts of coccidian oocysts per gram of feces were recovered in weaners than in growers and adults rabbits (P < 0.001), rabbits that were kept in high density group housing (P < 0.05) and housing with more than two tiers.

Conclusion: This study identified group housing of rabbits of different ages and inadequate control of concurrent infections as the major risk factors associated with coccidiosis in domestic rabbits in Kenya.     

The Effect of Anthelmintic Capsules on the Egg Output and Larval Viability of Drug-resistant Parasites

Challenge with an equal mix of drug-resistant and drug-susceptible larvae of Teladorsagia circumcincta resulted in infections in groups of lambs (n = 6) either untreated or given controlled-release capsules, containing either albendazole or ivermectin. Lambs treated with albendazole capsules contained similar numbers of adult worms at necropsy to the other groups but had no detectable faecal egg count. Animals treated with ivermectin capsules had similar worm burdens and faecal egg counts to the control group but the worms had significantly higher numbers of eggs in utero. These results provide evidence for suppression of egg production by both anthelmintic treatments. The observation that albendazole caused a significant reduction in the developmental success of parasite eggs also has implications for the use of faecal egg count as an indicator for pasture contamination with resistant parasites. In two further groups of lambs, either untreated or given albendazole capsules, treatment caused a significant reduction in egg count and adult worm burden of Trichostrongylus colubriformis. No significant effects were observed on in utero egg counts or egg viability and the apparent effect on the number of eggs produced in faeces per adult female was not significant (p = 0.077). There was, therefore, no evidence that albendazole controlled-release capsules caused suppression of egg output in this species.     

Efficacy of Hydrogen Peroxide to Control Parasitic Infestations on Hatchery-Reared Fish

Abstract

The efficacy of hydrogen peroxide to control external parasitic infestations on juvenile (10–33-g) rainbow trout Oncorhynchus mykiss was evaluated in three clinical field trials. Fish were exposed to hydrogen peroxide concentrations ranging from 0 to 560 mg/L for 30 min once every other day for a total of three treatments. Pre- and posttreatment skin scrapes and gill wet mounts of test fish were microscopically examined to identify and enumerate external parasites. Infestation severity was classified as nonexistent (0 organisms), low (1–10 organisms), moderate (11–20 organisms), or high (?21 organisms). In trial 1, pretreatment skin examinations revealed a severe infestation of the protozoan Ambiphrya on all fish examined. Posttreatment skin examinations conducted within 24 h of the last treatment indicated that all hydrogen peroxide treatments eliminated Ambiphrya, whereas control fish remained severely infested with the protozoan. In trial 2, pretreatment examinations of skin and gill samples indicated a high infestation of the trematode Gyrodactylus (skin) and the protozoan Trichodina (gills) on all fish. Posttreatment examinations conducted within 24 h of the last treatment indicated that Gyrodactylus was eliminated from the skin of all treated fish; however, the high infestation of Trichodina remained on the gills of the test fish. All control fish had high infestation levels of both parasites. A high infestation of Ambiphrya was found on the skin of test fish before treatment (trial 3). Posttreatment examinations conducted 14 d after the last treatment revealed that 56% of the fish were parasite free, whereas the remaining test fish had low infestation levels. Control fish remained severely infested with the parasite. Based on the efficacy data, all hydrogen peroxide treatment regimens were efficacious in the control of Ambiphrya and Gyrodactylus.     

Effect of Ctenocephalides felis strongylus infestation on the performance of West African dwarf sheep and goats

Summary

A study of Ctenocephalides fells strongylus and of its effect on the performance of sheep and goats was made.

Fleas showed more affinity for sheep than goats. There was a high concentration between lamb and kid mortality and the degree of flea infestation. The clinical effects of flea infestation are highlighted. The factors responsible for flea infestation and its control are discussed.     

Ichthyophthirius multifiliis in Elvers and Small American Eels from the East River,Nova Scotia

Abstract

Elvers of American eels Anguilla rostrata entering the East River on the Atlantic coast of Nova Scotia between early May and the end of July were parasitized by Ichthyophthirius multifiliis during June of 1993 for the first time in 6 years of observation. Prevalence of infection in elvers (49.9–68.2 mm total length, TL) ranged from 7 to 30%; weekly mean prevalence (pooled sample) ranged from 13.0 to 23.3% over an infection period of 42 d. Weekly prevalence ranged from 8.3 to 12.2% for small eels (70–120 mm TL). Mean intensity of infection was 6.1 trophonts/host (range, 1–61) for elvers and 7.2 trophonts/host (range, 1–40) for small eels. Count distributions were right-skewed and leptokurtic for both elvers and small eels. No conclusion could be made (due to low statistical power) as to whether length or weight was related to mean intensity of parasitism in either elvers or small eels or whether mean intensity differed between elvers and small eels. High river discharge during June–July, but not water temperature (April–July), may have contributed to development of the epizootic of I. multifiliis in 1993.     

Involvement of Zoospores of Saprolegnia diclina (Oomycotina: Saprolegniaceae) in the Attachment to and Invasion of Eggs of Brook Trout under Experimental Conditions

Abstract

Colonization and infestation of live eggs of brook trout Salvelinus fontinalis by experimentally raised zoospores of Saprolegnia diclina was monitored with scanning electron microscopy from 5 min to 128 h postexposure. Within 10 min postinoculation, settled zoospores and encysted spores were observed on the surface of some of the eggs. Encysted spores were stuck to eggs by a surface-covering material. Within 15 min postinoculation, encysted spores germinated to form thalli that either spread over or penetrated the chAorionic membrane, or both. From 1 to 128 h postinoculation, egg surfaces were covered by mixtures of zoospores, encysted spores, and germlings, and by light to heavy mycelial mats of S. diclina     

Aspects of the pathology of Lamproglena clariae (Copepoda: Lernaeidae) on gills of Clarias gariepinus from the Vaal River system,South Africa

Lamproglena clariae attaches to gill filaments of Clarias gariepinus, penetrates the gill tissue and consumes blood. Hence, the purpose of this study was to investigate the mechanical damage caused by this parasite on gill filaments of the host. Infestation intensity and haematocrit values of fish blood were determined and correlated. Fish were killed, gills dissected out and observed with a dissection microscope. Gill filaments with adult females in situ were fixed in a solution of alcohol, formaldehyde and acetic acid and preserved in 70% ethanol. Fixed specimens were studied by histological examination following staining with Heidenhein’s azan solution. Gross morphology revealed varying degrees of swelling of gill filaments near the attached specimens of L. clariae. Epithelial hyperplasia, resulting in fusion of gill lamellae and necrosis of the host tissue in the vicinity of the parasite were revealed through histological examination. No correlation was evident between the infestation intensity and fish haematocrit values. Although results showed that L. clariae causes localized infestation, high intensity of infestation may be detrimental to the fish. Hyperplasia of epithelial tissue resulting in fusion of lamellae would result in restriction of air passages and thus hinder the process of respiration of the host.     

The prevalence of isospora suis and strongyloides ransomi in suckling piglets in the Netherlands

Summary

Faecal samples from suckling piglets from 113 litters on 25 farms in the Netherlands were examined to study the prevalence of gastrointestinal parasites, in particular Strongyloides ransomi and Isospora suis. S. ransomi was not found but I. suis was demonstrated in 17 of the 25 farms and in 41 out of 77 litters of these farms (53%). No other parasites were found. On the basis of these results, a longitudinal study on the incidence and significance of I. suis was performed on 10 farms (5 litters/farm). I. suis was found on 9 out of 10 farms and in 56% of the litters. Farms differed in infection levels, measured as the numbers of patent litters, and in the onset of patency. Other parasites were only found in faecal samples from the sows and from farrowing pens. These were, in order of prevalence, Balantidium coli, Ascaris suum, Eimeria spinosa, E. debliecki and E. suis.     

Canine Leishmaniasis: Parasitological Follow-up of the Treated Subject

A cross-sectional study was carried out to determine the prevalence of gastrointestinal (GI) nematodes and flukes (Fasciola and amphistomes) infection in communally grazed traditional cattle, zero-grazed small-scale dairy cattle and intensively grazed large-scale dairy cattle through examination of helminth eggs in faeces. Results indicated that the type of management, especially the grazing habit, has a significant influence on the prevalence and intensity of GI nematodes and flukes. The prevalence of GI nematodes in traditional, large-scale dairy and small-scale dairy cattle was 67%, 44.4% and 37%, respectively, with the highest faecal egg counts in calves. The overall prevalence of Fasciola gigantica in traditional, large-scale dairy and small-scale dairy cattle was 63.8%, 46.2% and 28.4%, respectively. The prevalence of amphistomes was 81.9%, 55.5% and 41.1% in traditional, large-scale dairy and small-scale dairy cattle, respectively. The high prevalence of flukes in the traditional system was attributed to communal grazing and watering management practices. Stomach flukes recovered in examined cattle at the abattoir were Calicophoron microbothrium and Cotylophoron jacksoni. About 42.1% of infected animals had both Fasciola and amphistomes. The prevalence of both GI nematodes and flukes varied greatly among villages and farms. The prevalence of both Fasciola and amphistomes was higher in adults (58.5%, 75.2%) than in yearlings (36.5%, 51.5%) or calves (24.9%, 47.2%). The variation in the prevalence of both GI nematodes and flukes among management and age groups within systems can be used as an entry point towards rational use of anthelmintics for each management system. More studies on seasonal transmission pattern of all these parasites are required in order to design rational, economic and locally sustainable parasite control programmes.     

An investigation into the epidemiology of Strongylidae infections in the horse in the Netherlands

Summary

In a four‐year survey, the course of pasture infestation with infective larvae of Strongylidae and the pattern of development of the Strongylidae infection in the host were investigated. In this way it was hoped to obtain epidemiological data which might serve as a basis for the control of strongylidosis in the horse.     

Schistosoma mattheei in the ox: Observations on the parasite

Nineteen Friesian steers infested with between 5 000 and 45 000 cercariae of Schistosoma mattheei were slaughtered at intervals between 7 and 107 weeks post-infestation and the parasites were recovered by perfusion of the blood vessels. Adult parasites were eliminated as infestation progressed, the greatest loss occurring between 18 and 40 weeks. Females in the mesentery became shorter as infestation progressed but males remained unchanged. Males from the gastric veins were sometimes longer than those from the mesentery while males and females from liver and lungs were often shorter. Females from the mesentery contained 0–107 eggs, with a mean of 36, and those from liver and lung contained fewer eggs. The prepatent period was 6–7 weeks. A sharp reduction in faecal egg count between 15 and 25 weeks post-infestation was caused by a reduction in oviposition. The marked changes in the number of parasites present, their length and their egg-laying capacity appeared to be mediated by the immune response of the host and were manifestations of the establishment of a biological equilibrium which limited the pathogenic effects of the parasite.     

Proliferative Gill Disease of Fish from the Tennessee-Tombigbee Waterway,Mississippi

Abstract

Proliferative gill disease (PGD), a condition not previously reported in wild fish, was found in two channel catfish Ictalurus punctatus sampled from the Tennessee-Tombigbee Waterway in Mississippi during June and July 1989. The parasite thought to cause PGD was observed in only one of the fish, but the distinctive lesions associated with this disease were prominent in both of the channel catfish. Organisms resembling the PGD parasite were also found in the gills of 4 of 18 largemouth bass Micropterus salmoides and 6 of 20 bluegills Lepomis macrochirus, but there was little or no host response to these parasites.     

Egg transmission of egg drop syndrome 1976 virus in fowl

Summary

Egg transmission of egg drop syndrome 1976 virus (BC14 virus) in fowl was demonstrated in the second and third week after experimental infection. Eggs of BC14 virus infected hens were incubated weekly after disinfection with formaline gas. After 18 days of incubation, eggs with live embryos were homogenized. This egg material was fed to adult hens, housed in isolators.

Seroconversion in these birds demonstrated egg transmission.

It is suggested that egg transmission occurs as a result of viremia.