The role of density-dependent arrested larval stages on parasite dynamics and stability: Lessons from nematodes and donkeys

Welfare assessment of Thoroughbred horses naturally infected with gastrointestinal parasites in Southern Brazil: Quantifying the host-parasite relationship

Horse welfare assessment (HWA) does not account for individual or herd parasite infection. This study investigated the connection between HWA and individual parasite fecal egg count (FEC) in 90 Thoroughbred horses. All horses were naturally infected with gastrointestinal parasites and were evaluated for individual welfare indicators and FEC monthly, for 12 months. Horses were divided into three groups of 30 mares, 30 foals aged between 13 and 16 months (G2013), and 30 foals aged between two months and one year (G2014). A horse welfare protocol was developed and 1024 assessments were carried out by five trained assessors. FEC ranged from 0 to 5,760 with 98.8 % showing small strongyle eggs. Body condition scores were ideal in 94.4 % of the evaluations (n = 967), and 95.8 % of all horses had good clinical and behavioral indicators. Despite the variation in FEC, the data found no significant association between FEC and the behavioral indicators. The study suggests that FEC alone should not be used as a determinant of welfare when animals are managed with good nutritional and health management practices.

Use of Flubendazole and Fenbendazole for Treatment of Lung Severe Infection by the Gapeworm Cyathostoma bronchialis (Nematoda: Syngamidae) in Branta hutchinsii, Anser indicus and B. leucopsis Exotic Geese: An Interesting Case

A 6-year-old female goose (Branta hutchinsii) from a group of ornamental exotic geese was found dead due to severe respiratory failure, followed by emission of haemorrhagic sputum and blood clots from the beak and nostrils, and then collapse. At necropsy, the cause of death was attributed to a total of 76 helminth parasites found in the trachea and lungs, then identified as Cyathostoma bronchialis. The flock was initially treated by feed with flubendazole (1200 g/1000 kg/feed) for 7 consecutive days but, at the reappearance of the respiratory symptoms 10 days after, the animals were given fenbendazole by drinking water (300 mg/L) for 7 consecutive days, but at the reappearance of the respiratory symptoms 10 days after, the animals were given fenbendazole via drinking water (300 mg/L) for 7 consecutive days. Despite these treatments, the respiratory symptoms continued to relapse 10-15 days after the end of drug administration. In the literature, there are no data regarding drugs for the treatment of C. bronchialis infestations in geese, and the use of these drugs in exotic birds occurs as "off-label" use. This case study provides information on C. bronchialis life cycle, which is still poorly studied and poorly documented today. In particular, the case provides useful suggestions for evaluating an appropriate protocol for the treatment of C. bronchialis in geese.

Intestinal Strongyle Genera in Different Typology of Donkey Farms in Tuscany, Central Italy

Intestinal strongyles are common helminths of donkeys, in which they may be responsible for disease and poor performance. This study aimed to identify intestinal strongyle genera in 55 naturally infected donkeys from three different farm typologies in Tuscany, central Italy, using morphological and metrical analysis of third stage larvae (L3) obtained from faecal cultures. Larvae were identified using two previous reported morphological identification keys. Moreover, eggs per gram (EPG) data were also evaluated to assess differences, if any, according to the farm typology, sex, and age of the examined donkeys. The results showed that small strongyles were prevalent in all donkey farms. In all examined farms, most (92–100%) of L3 were identified as cyathostomin species of the genera Cylicocyclus spp. and Cylicostephanus spp. Large strongyles of the genera Strongylus spp. and Triodontophorus spp., were identified at low percentage (8%), only in the single organic farm included in the study. A high agreement was observed between the two different morphometric keys used. No significant differences were found for EPG according to farm typology, and sex and age from the examined donkeys. This is the first report about genera identification of intestinal strongyles infecting donkeys in Tuscany, Italy.

A model for the dynamics of the parasitic stages of equine cyathostomins

A model was developed to reproduce the dynamics of the parasitic stages of equine cyathostomins. Based on a detailed review of published literature, a deterministic simulation model was constructed using the escalator boxcar-train approach, which allows for fully-overlapping cohorts of worms and approximately normally distributed variations in age/size classes. Key biological features include a declining establishment of ingested infective stage larvae as horses age. Development rates are constant for all the parasitic stages except the encysted early third stage larvae, for which development rates are variable to reflect the sometimes extended arrestment of this stage. For these, development is slowed in the presence of adult worms in the intestinal lumen, and when ingestion of infective larvae on herbage is high or extended. In the absence of anthelmintic treatments, the life span of adult worms is approximately 12 months, and the presence of an established adult worm burden largely blocks the transition of luminal fourth stage larvae to the adult stage, resulting in mortality of the larvae. This inhibition is removed by effective anthelmintic treatment allowing the rapid replacement of adult worms from the pool of mucosal stages. Within the model, the rate and seasonality at which infective stage larvae are ingested strongly influences the dynamics of the pre-adult stages. While the adult worm burden remains relatively stable within a year, due to the negative feedback they have on developing stages, the numbers and proportions of larval stages relative to the total worm burden increase with the numbers of infective larvae ingested. Further, within the model, the seasonal rise and fall of encysted stages is largely driven by the seasonal pattern of infective larvae on pasture. Because of this, the model reproduces the contrasting seasonal patterns of mucosal larvae, typical of temperate and tropical environments, using only the appropriate seasonality of larvae on pasture. Thus, the model reproduces output typical of different climatic regions and suggests that observed patterns of arrested development may simply reflect the numbers and seasonality of free-living stages on pasture as determined by different management practices and weather patterns.

Are small strongyles (Cyathostominae) involved in horse colic occurrence?

Strongyle infections have been traditionally regarded as a possible cause of colic in horses. Aim of the study was the comparison of parasitological status between subjects with or without colic syndrome, with particular attention to small strongyle infections. Coprological analyses were performed on 86 horses: 43 with colic and 43 controls. Strongyle eggs were found in 34/86 horses (prevalence 39.5%), the mean number of strongyles eggs per gram of faeces (EPG)² was 145.34 (standard deviation 398.28). All those 34 positive animals had small strongyles infections. Negative binomial multiple regression highlighted no influence of horse sex on strongyle EPG, while there was a negative relationship between age and EPG (p <0.05); the same analysis revealed a significant difference of EPG (p <0.05) between control horses (mean EPG=178.1; standard deviation: 411.4) and horses with surgical colic (mean EPG=68.6 standard deviation: 259.8) when controlling for S. vulgaris presence including it in the model. On the contrary, the intensity of infection in horses with non-surgical colic (mean EPG=154.5; standard deviation: 480.4) did not significantly differed from controls. Similar results were obtained having estimated cyathostomine EPGs as dependent variable. Multinomial logistic regression confirmed the negative relationship between cyathostonine presence and surgical colic occurrence. It is possible that (1) the presence of adult luminal parasites, would have a protective effect against the pathogenic action exerted by the development and emergence of small strongyles larvae from intestinal mucosa; (2) the management practices able to reduce the risk of colics are the same that cause higher exposure to strongyle infective larvae.