The detection of anthelmintic resistance in nematodes of veterinary importance

Before revised World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines on the detection of anthelmintic resistance can be produced, validation of modified and new methods is required in laboratories in different parts of the world. There is a great need for improved methods of detection of anthelmintic resistance particularly for the detection of macrocyclic lactone resistance and for the detection of resistant nematodes in cattle. Therefore, revised and new methods are provided here for the detection of anthelmintic resistance in nematodes of ruminants, horses and pigs as a basis for discussion and with the purpose that they are evaluated internationally to establish whether they could in the future be recommended by the WAAVP. The interpretation of the faecal egg count reduction test has been modified and suggestions given on its use with persistent anthelmintics and continuous release devices. An egg hatch test for benzimidazole (BZ) resistance is described. A microagar larval development test for the detection of benzimidazole and levamisole resistance provides third stage larvae for the identification of resistant worms. The sensitivity of these two tests can be increased by using discriminating doses rather than LD(50) values. Details are given of a PCR based test for the analysis of benzimidazole resistance in strongyles of sheep and goats, horses and cattle. Although promising for ruminant trichostrongyles, quantitative determination of gene frequency using real time PCR requires further development before PCR tests will be used in the field. Apart from faecal egg count reduction tests there are currently no satisfactory tests for macrocylic lactone resistance despite the great importance of this subject. Except for treatment and slaughter trials there are no validated tests for fasciolicide resistance or for the detection of resistance in cestodes.     

Genotyping of Toll-like receptor 4, myeloid differentiation factor 2 and CD-14 in the horse: an investigation into the influence of genetic polymorphisms on the LPS induced TNF-alpha response in equine whole blood

The inter- and intra-species differences in the response to lipopolysaccharides (LPS) are well recognised in mammalian species. It has been hypothesized that these differences can be attributed to genetic polymorphisms in the components involved in LPS signal transduction. These components include the cluster of differentiation factor 14 (CD-14), a membrane bound protein on the surface of mononuclear cells that recognises LPS and a receptor complex consisting of Toll-like receptor-4 (TLR-4) and myeloid differentiation factor-2 (MD-2). Sequencing of these three proteins in humans and mice revealed that all three are susceptible to polymorphic alterations, influencing the response to LPS. Previous experiments in the horse showed large inter-individual variations in the response to LPS. With the aim to assess this inter-individual variation, we performed a whole blood assay in 10 healthy horses as a functional assay to study the responsiveness to LPS. In 3 out of the 10 horses, LPS-induced TNF-alpha production was significantly lower compared to the overall mean. Subsequently the entire cDNA sequence encoding for the TLR-4, MD-2 and CD-14 protein was documented for each horse. Although mutations were observed in the sequence of TLR-4, these could not be related to an altered response to LPS in the concentration used in this study, as determined in the whole blood assay. Despite the various mutations found in the TLR-4 receptor protein, no alterations could be found in either the MD-2 or CD-14 gene, which are obviously more conserved structures.     

Cutaneous transmissible venereal tumor without genital involvement in a prepubertal female dog

An 11-month-old prepubertal crossbreed female dog was presented with multiple nodular lesions disseminated over the cervical, back, flank, and abdominal regions. The lesions were ulcerated and cauliflowerlike, or nodular and subcutaneous, measuring up to 13 cm in diameter. Cytologic preparations of one of the lesions revealed a uniform population of round to oval cells, with lightly basophilic cytoplasm that contained multiple distinct vacuoles. Frequent mitotic figures and occasional lymphocytes were also observed. The cytologic diagnosis was cutaneous transmissible venereal tumor (TVT) in a progressing growth phase. This was confirmed by histologic and immunohistochemical findings. Vaginal TVT was diagnosed later in the dog's mother. TVT is a contagious neoplasm of sexually mature dogs that usually is transmitted by coitus and affects the genital mucosa. To our knowledge, this is the first report of naturally occurring multicentric TVT in a prepubertal female dog and also is unique in its exclusively cutaneous (no mucosal) involvement. We speculate that transmission of neoplastic cells occurred during cohabitation and social/mothering behavior between the dogs. Despite the atypical clinical presentation, response to chemotherapy with vincristine was excellent, leading to complete regression of the neoplasm without relapse after 6 months.     

Thermoregulation of the testicle in response to exercise and subsequent effects on semen characteristics of stallions

Stallions (n = 8) were implanted with a thermal sensory device in the muscle of the neck and the subcutaneous tissue of the scrotum and then assigned to either a nonexercise (Non-EX; n = 4) or exercise (EX; n = 4) group. A motorized equine exerciser was used to work EX stallions 30 min/d for 4 d/wk during a 12-wk period from July through October 2010. Temperatures (subcutaneous scrotal, intramuscular neck, and rectal) were recorded at 0, 22, and 30 min after the start of exercise, as well as 60 and 120 min post-exercise. Hourly ambient temperature and relative humidity data were also obtained. Semen was collected at 0, 4, 8, and 12 wk and analyzed for volume, sperm concentration, total sperm numbers, percentages of total and progressively motile sperm, sperm morphologic characteristics, and sperm DNA quality. No effect (P > 0.05) of exercise was observed on any of the measured semen variables. Implantation of thermal sensory devices had no demonstrable acute or chronic effects on the scrotal or neck tissue, indicating that the thermal sensory devices are a safe and effective way to measure subcutaneous scrotal and neck temperatures. At 22 and 30 min of exercise, rectal and neck temperatures increased (P < 0.0001) approximately 1.9 and 2.4°C, respectively, and scrotal temperatures simultaneously increased, although not significantly (P = 0.33), approximately 0.8°C. Correlations existed between scrotal, neck, rectal, and ambient temperatures, with the correlation between scrotal and rectal temperatures being greatest (r(s) = 0.76; P < 0.0001). Although moderate exercise for a short duration in extreme heat and humidity did significantly increase core body temperatures in stallions, scrotal temperatures did not significantly increase, and sperm parameters were unaffected.     

Polymelous layer chick displaying additional malformations of the hind gut: case report and in-depth review of related literature

A case report of a male 6-day-old male layer chick featuring incomplete polymelia of the hind limbs and hindgut malformations is presented. The chick was submitted to computed tomography (CT) examination and subsequent anatomical dissection. Apart from the two supernumerary hind limbs, the anatomical dissection revealed additional hindgut alterations: three uniform-sized caeca flanked the ileum, and the rectum branched into paired cloacae. The supernumerary hind limbs were localized caudal to the normal hind limbs in an inverted position and were attached to pelvic girdle elements and to a curtate pygostyle. They featured a prominent unpaired femur besides paired tibiotarsi, tarsometatarsi and species-specific phalanges of the toes. Additionally, two separate bones attached to the caudoventral aspect of the regular hip bones were developed. The supernumerary limbs were in part mobile and received nerve and vascular supply. Digital 3D-reconstruction based on the CT datasets revealed the osseous components of the malformed body parts. The possible morphogenesis including an in-depth literature review and the clinical implications of the reported malformations are discussed.     

Outbreak of abdominal distension and obstipation in a C57BL/6J experimental autoimmune encephalomyelitis study

Seventy-four 9-week old female C57BL/6J mice housed in a conventional facility were manipulated to induce experimental autoimmune encephalomyelitis, among which 26 developed clinical signs including lethargy, absence of defecation, and abdominal distension. By gross necropsy examination, there was distension of the cecum and colon with fecal impaction. By histologic examination, there was severe ulcerative and proliferative typhlocolitis. Fecal ELISA confirmed the presence of toxins A and B of Clostridium difficile. Alteration in immune status of the immunocompetent mice, due to stress caused by experimental manipulation or autoimmune disease, may have led to intestinal dysbiosis, followed by opportunistic infections resulting in C. difficile-associated disease. This report brings to light the occurrence of the disease in immunocompetent laboratory mice during experimental manipulations associated with alteration in immune status, and it discusses potential hazards associated with conventional housing within a hospital-associated research institute.     

Early experience with diverse foods increases intake of nonfamiliar flavors and feeds in sheep

This study determined whether early experiences by sheep with monotonous or diverse diets influence intake of unfamiliar flavors and feeds later in life. Thirty 2-mo-old lambs were randomly assigned to 3 treatment diets (n = 10): diverse (DIV), diverse with plant toxins (DIV+T), and monotonous (MON). Lambs in DIV received in 9 successive periods of exposure 4-way choice combinations of 2 foods high in energy and 2 foods high in protein from an array of 6 foods: 3 high in energy [beet pulp, oat grain, and a mix of milo:grape pomace (60:40)] and 3 high in digestible protein (DP) (soybean meal, alfalfa, corn gluten meal). Lambs in DIV+T received the same exposure as DIV, but 2 plant toxins, oxalic acid (1.5%) and quebracho tannins (10%), were randomly added to 2 of the feeds in each of the choice combinations. Lambs in MON received a monotonous balanced diet, made with a mixture of all 6 feeds detailed before. All treatments received their feed in 4 separate buckets. During exposure, treatments did not differ in total daily DMI (P = 0.31), but daily intake of ME was less (P < 0.02) and daily intake of DP was greater (P < 0.03) for lambs in DIV and DIV+T than for lambs in MON. Treatments did not differ in ADG or G:F (P > 0.05). After exposure, lambs were offered a familiar feed (wheat bran) containing novel flavors (maple, garlic, or bitter) and 2-way choices of novel feeds (fescue hay vs. corn distillers grains, rice vs. calf manna, and green peas vs. rolled oats). Intake of maple-flavored wheat bran tended (P = 0.08) to be greater for lambs in DIV than for lambs in DIV+T and MON. Intake of bitter-flavored and garlic-flavored wheat bran were greater (P = 0.03 and P = 0.04, respectively) for lambs in DIV and DIV+T than for lambs in MON. During 2-way choice trials, lambs in DIV, but not in DIV+T, showed greater intakes of fescue hay (P = 0.05) and rice (P = 0.04) than lambs in MON. Intake of green peas was greater (P = 0.03) for lambs in DIV and DIV+T than for lambs in MON. At the end of testing, lambs in DIV but not in DIV+T showed greater ADG than lambs in MON (P = 0.05). Thus, early exposure to diverse foods enhanced acceptance of novel flavors relative to early exposure to a monotonous ration. Early experience with diverse feeds plus plant toxins led to a less diverse diet than early experience with diverse feeds. Early exposure to diverse feeds may be beneficial in production systems that require rapid acceptance and high intake of unfamiliar feeds.