An initial investigation of the predatory activity of the phoretic mites of dung beetles, Macrocheles sp. (Mesostigmata: Macrochelidae), on the gastrointestinal nematode of sheep Haemonchus contortus (Strongylida: Trichostrongylidae)

Stool collection is part of routine veterinary procedures and does not involve any procedures that could be traumatic to the sheep. As such procedures do not constitute animal experimentation involving vertebrates according to French laws, no specific ethics clearance was required.International audienceHighlights: • Dung beetles’ phoretic mites may act as predators of Haemonchus contortus larvae. • In vitro, these mites can reduce the development of this pathogenic nematode. • Controlling the nematode Haemonchus contortus through its free living stages.Abstract: Worldwide increasing levels of anthelmintic resistance are pushing farmers and health advisors towards a more sustainable management of gastrointestinal nematodes (GIN), one of the greatest threats to the viability of grazing small ruminant production systems, and to these animals’ welfare. These Strongyloidea develop freely in livestock dung, where they are exposed to predatory organisms that can eventually break their cycle. The aim of this study was to investigate the effect of phoretic mites of dung beetles Macrocheles sp. (Macrochelidae) on the gastrointestinal nematode Haemonchus contortus (Rudolphi, 1803) that has a free-living larval stage that evolves in sheep feces. Direct observations under a stereomicroscope confirmed that the studied Macrocheles mites may have an active predatory behavior on the third-stage (L3) larvae of H. contortus. In order to quantify the effects of the mites’ predation on the survival of L3 nematode larvae, we designed experimental units, replicated across five trials, and containing free-living stages of the nematode either in the presence or absence of mites. The number of H. contortus larvae that reached the third-stage was significantly reduced in the presence of mites, despite a variable intensity of the predatory effects between trials. This is the first report of a predatory activity of phoretic mites of dung beetles’ on a livestock gastrointestinal nematode. This first step encourages further studies in order to have a better quantification of this interaction, and to investigate to which extent the phoretic mites of dung beetles can impact H. contortus populations in natural conditions.Graphical abstract:https://ars.els-cdn.com/content/image/1-s2.0-S1049964423001548-ga1.jp

Daily sodium cromoglycate treatment decreased mast, cell and blood eosinophilic responses in Haemonchus contortus resistant Black Belly sheep.

International audienc

Selection of sheep for resistance to gastro-intestinal nematodes in France: where are we and where are we going?

International audienc

Attractiveness and Specificity of Different Polyethylene Blue Screens on Stomoxys calcitrans (Diptera: Muscidae)

International audienceSimple Summary: The haematophagous fly Stomoxys calcitransis considered as a major pest of livestock worldwide. Insecticides have been extensively used to control this pest but resistance to these chemical compounds is now reported in many countries. Therefore, a more sustainable and efficient control is needed. New blue polyethylene sticky screens have been proved to be very attractant for stable flies. They are produced at a lower price than all blue fabric screens or traps. More than 70% of flies are captured on the lower half (30 to 60 cm above ground) of the screens. In our conditions, very few non-target fauna was captured as very few pollinators were caught by these screens. These results are highlighting the interest of these blue polyethylene screens to control stable flies in cattle farms, in comparison with more expensive blue fabrics. Stomoxys calcitrans is considered as a major pest of livestock worldwide. Insecticides have been extensively used to control this pest but resistance to these chemical compounds is now reported in many countries. Therefore, a more sustainable and efficient control is needed. Seven different types of blue screens, with reflectances around 460 nm, were tested during summer 2016 in southwestern France to evaluate their attractiveness and their specificity for stable flies. Height of the screen and orientation (east or west) of a blue screen were also considered. High levels of S. calcitrans captures were recorded during this study (from 141 to 7301 individuals per blue screen and per day) whereas the numbers of tabanids and pollinator insects remained extremely low (less than 10 individuals per screen and per day). No significant difference in attractiveness has been shown between the different types of blue screens. The lower half of the blue screens caught significantly more stable flies (70%) than the higher half (30%). The “east” side of the screen attracted 60% of stable flies but this was not significantly different from the west side. These results are highlighting the interest in these blue polyethylene screens for controlling stable flies in cattle farms, in comparison with more expensive blue fabrics

La sélection génétique d'ovins résistants aux strongles gastro-intestinaux en France : mythe ou réalité ?

National audienc

Experimental infections of rabbits with proliferative and latent stages of Besnoitia besnoiti

International audienceCattle besnoitiosis due to Besnoitia besnoiti is spreading across Europe and is responsible for severe economic losses in newly infected herds. Experimentally speaking, rabbits have been found to be susceptible to this parasite. The adaptation of B. besnoiti to rabbits may offer a new, easier and cheaper model of investigation for this disease. This study compared the virulence between tachyzoites and bradyzoites of B. besnoiti in rabbits. Eighteen New Zealand rabbits were allocated into three groups of six animals each. The rabbits from the control (group C), "tachyzoite" (group T) and "bradyzoite" (group B) groups were subcutaneously injected in the right flank with 66 mu g of ovalbumin, 6.10(6) tachyzoites (125th passage on Vero cells) and 6.10(6) bradyzoites (collected from a natural infected cow) of B. besnoiti, respectively. Clinical follow-up and blood sampling for serological survey and qPCR were performed during 10 weeks until euthanasia. Molecular and immunohistochemistry examination was achieved on 25 samples of tissue per rabbit. Seroconversion occurred in group T without any clinical signs. Rabbits of group B exhibited a febrile condition (temperature above 40 A degrees C from day 8 to day 11 following injection) with positive qPCR in blood. Cysts of B. besnoiti were found on skin samples and organs of rabbits from group B in tissue explored with threshold cycle (Ct) values below 30. These results suggest a higher virulence of bradyzoites in rabbits than Vero cell-cultivated tachyzoites. The proposed model could be used to assess the in vivo effectiveness of vaccine or drugs against cattle besnoitiosis

In vitro pre-exposure of Haemonchus contortus L3 to blood eosinophils reduces their establishment potential in sheep

Different authors have reported that eosinophils are capable of immobilising infective larvae of different species of nematodes in vitro. However, classifying larvae as mobile or immobile is so subjective that it does not always mean all apparently immobile larvae are dead or those that are mobile are capable of surviving further immune responses if administered to their natural hosts. The objective of this experimental study was therefore to substantiate the role of eosinophils in the killing of Haemonchus contortus infective larvae by comparing the infectivity in sheep of larvae that had been incubated with eosinophil-enriched cell suspensions with control larvae. Since it was not possible to isolate pure eosinophils from sheep blood, we were compelled to evaluate the effects of other blood cells contaminating our eosinophil-enriched suspensions. Although eosinophils and neutrophils were the only cells found adherent to H. contortus infective larvae in vitro, induced eosinophils in the presence of immune serum were primarily responsible for the drastic reduction in larval motility compared to the minor effects of neutrophils and mononuclear cells. Corresponding reductions in faecal egg count and worm numbers were observed when the incubated larvae were transferred intra-abomasally to sheep. Interestingly, the proportion of larvae that failed to establish was much higher following incubation with induced eosinophils compared with other cells or with immune serum alone. Although this study did not address the in vivo role of eosinophils in sheep, the results strongly indicate that sheep blood eosinophils have a larval killing potential in vitro, and a larval mobility test alone may not fully explain the level of damage inflicted on the larvae

In vitro pre-exposure of Haemonchus contortus

International audienceDifferent authors have reported that eosinophils are capable of immobilising infective larvae of different species of nematodes in vitro. However, classifying larvae as mobile or immobile is so subjective that it does not always mean all apparently immobile larvae are dead or those that are mobile are capable of surviving further immune responses if administered to their natural hosts. The objective of this experimental study was therefore to substantiate the role of eosinophils in the killing of Haemonchus contortus infective larvae by comparing the infectivity in sheep of larvae that had been incubated with eosinophil-enriched cell suspensions with control larvae. Since it was not possible to isolate pure eosinophils from sheep blood, we were compelled to evaluate the effects of other blood cells contaminating our eosinophil-enriched suspensions. Although eosinophils and neutrophils were the only cells found adherent to H. contortus infective larvae in vitro, induced eosinophils in the presence of immune serum were primarily responsible for the drastic reduction in larval motility compared to the minor effects of neutrophils and mononuclear cells. Corresponding reductions in faecal egg count and worm numbers were observed when the incubated larvae were transferred intra-abomasally to sheep. Interestingly, the proportion of larvae that failed to establish was much higher following incubation with induced eosinophils compared with other cells or with immune serum alone. Although this study did not address the in vivo role of eosinophils in sheep, the results strongly indicate that sheep blood eosinophils have a larval killing potential in vitro, and a larval mobility test alone may not fully explain the level of damage inflicted on the larvae

Asymptomatic

Protozoan parasites of the Cryptosporidium genus cause severe cryptosporidiosis in newborn lambs. However, asymptomatic infections also occur frequently in lambs and ewes. In sheep, the most commonly detected Cryptosporidium species are C. ubiquitum, C. xiaoi and C. parvum. Due to a lack of relevant information about such infections in France, we investigated the situation on five dairy sheep farms in the Pyrénées-Atlantiques Department in south-western France in December 2017. Individual fecal samples were collected from 79 female lambs (5–17 days old) and their mothers (72 ewes). Oocysts were screened using Heine staining before and after Bailenger concentrations. Cryptosporidium species identification and genotyping were performed using real-time PCR and gp60 gene sequencing. No cases of clinical cryptosporidiosis were observed in the 79 lambs. Microscopically, Cryptosporidium spp. oocysts were observed in only one lamb on one farm (prevalence 1.3%) and one ewe on another farm (prevalence 1.4%). By contrast, Cryptosporidium spp. DNA was detected in 17 ewes (prevalence ranging from 10.5% to 50% depending on the farm) and in 36 lambs (prevalence ranging from 0% to 77.8% depending on the farm). Only zoonotic Cryptosporidium parvum IId and IIa genotypes were identified when genotyping was possible. Cryptosporidium ubiquitum and C. xiaoi were detected on one and three farms, respectively. We conclude that healthy young lambs and their mothers during the peripartum period could be a source of environmental contamination with oocysts