Amphistomes.

Amphistomes, commonly referred to as 'stomach' or 'rumen' flukes because of the localization of these flukes in the stomach of ruminants, are digenetic trematodes distinguished by the absence of an oral sucker and the position of the ventral sucker or acetabulum at the posterior end of the body. The body is characterized by leaf-like fleshy structure, pink or red in colour with a large posterior sucker. Amphistomes are an important group of parasites since they cause 'amphistomiasis' (variously known as paramphistomosis/amphistomosis), a serious disease of great economic importance in ruminants worldwide. These parasites have a broad spectrum of definitive hosts together with a wide geographical distribution. Though, they form a continuous evolutional lineage from fishes to mammals, amphistomes mainly inhabit the rumen and reticulum of ruminant mammals, while some species occur in the large intestine or parenteric sites of ruminants, pigs, equines and man.

Abomasal dysfunction and cellular and mucin changes during infection of sheep with larval or adult Teladorsagia circumcincta.

This is the first integrated study of the effects on gastric secretion, inflammation and fundic mucins after infection with L3 T. circumcincta and in the very early period following transplantation of adult worms. At 3 months-of-age, 20 Coopworth lambs were infected intraruminally with 35,000 L3; infected animals were killed on Days 5, 10, 15, 20 and 30 post-infection and 6 controls on either Day 0 or 30 post-infection. Another 15 Romney cross lambs received 10,000 adult worms at 4-5 months-of-age though surgically-implanted abomasal cannulae and were killed after 6, 12, 24 and 72 hours; uninfected controls were also killed at 72 hours. Blood was collected at regular intervals from all animals for measurement of serum gastrin and pepsinogen and abomasal fluid for pH measurement from cannulated sheep. Tissues collected at necropsy were fixed in Bouin's fluid for light microscopy, immunocytochemistry and mucin staining and in Karnovsky's fluid for electron microscopy. Nodules around glands containing developing larvae were seen on Day 5 p.i., but generalised effects on secretion occurred only after parasite emergence and within hours after transplantation of adult worms. After L3 infection, there were maximum worm burdens on Days 10-15 post-infection, together with peak tissue eosinophilia, inhibition of gastric acid secretion, hypergastrinaemia, hyperpepsinogenaemia, loss of parietal cells, enlarged gastric pits containing less mucin and increased numbers of mucous neck cells. After adult transplantation, serum pepsinogen was significantly increased after 9 hours and serum gastrin after 18 hours. Parallel changes in host tissues and the numbers of parasites in the abomasal lumen suggest that luminal parasites, but not those in the tissues, are key drivers of the pathophysiology and inflammatory response in animals exposed to parasites for the first time. These results are consistent with initiation of the host response by parasite chemicals diffusing across the surface epithelium, possibly aided by components of ES products which increased permeability. Parietal cells appear to be a key target, resulting in secondary increases in serum gastrin, pit elongation, loss of surface mucins and inhibition of chief cell maturation. Inflammation occurs in parallel, and could either cause the pathology or exacerbate the direct effects of ES products.

Toxoplasma gondii infection in llama (Llama glama): acute visceral disseminated lesions, diagnosis, and development of tissue cysts.

Clinical toxoplasmosis has been reported in many species of warm-blooded animals but is rare in camelids. Here we report acute fatal systemic toxoplasmosis involving heart, thyroid gland, stomach, intestine, diaphragm, kidneys, adrenal glands, and liver of a 13-mo-old llama (Llama glama). Many Toxoplasma gondii tachyzoites were associated with tissue necrosis in multiple organs. Death was attributed to severe myocarditis. Ulcers associated with numerous tachyzoites were present in the C3 compartment of the stomach. Tissue cyst development was followed using bradyzoite-specific T. gondii antibodies. Individual intracellular, and groups of 2 or more, bradyzoites were identified in hepatocytes, biliary epithelium, myocardiocytes, lung, diaphragm, thyroid gland, spleen, and stomach. Lesions in the brain were a few microglial nodules and very early tissue cysts containing 1-3 bradyzoites. These observations suggest that the animal had acquired toxoplasmosis recently. Diagnosis was confirmed immunohistochemically by reaction with T. gondii -specific polyclonal rabbit serum but not with antibodies to the related protozoan Neospora caninum . Genetic typing using the DNA extracted from paraffin-embedded myocardium of llama and 10 PCR-restriction fragment length polymorphism (RFLP) markers revealed a type II allele at the SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, PK1 L358, and Apico loci; therefore, this isolate belongs to the ToxoDB PCR-RFLP genotype #1, which is most common in North America and Europe.

[Drug resistance makes new control measures of stomach parasites in small ruminants necessary]. / Resistentie maakt nieuwe aanpak van de bestrijding van maagdarmwormen bij kleine herkauwers noodzakelijk.

Control of parasitic gastroenteritis in small ruminants is threatened by the worldwide growing problem of anthelmintic resistance. Therefore, alternative approaches for worm control are imperative. Of utmost importance is to slow down selection pressure for anthelmintic resistance by using alternative control measures combined with minimal anthelmintic usage. New control options for the Netherlands are discussed.

Species diversity of nematode communities in the digestive tract of domestic ruminants: multivariate versus univariate estimations.

The evaluation of species diversity can be performed using species richness (number of species), diversity (number and relative proportions of species) or evenness (equitability of the proportion of each species). A large number of indices related to diversity or evenness is available but their mathematical properties remain unexplained, and hence their use is somewhat unreliable. We intended to present an array of well defined methods, based on discriminant analysis, to evaluate diversity in helminth communities of ruminants. The database used concerned seven cattle farms and seven sheep farms located in temperate areas, from which at least three necropsies were undertaken in autumn. The hosts were chosen because they had experienced nearly a complete grazing period and no anthelmintic treatment was performed for a minimum of 2 months before the necropsies were undertaken, so that the helminth communities could be considered as representative of each farm at one specific moment. We used discriminant analyses to evaluate diversity, based either on proportions of species, or on proportions of species arranged in decreasing order, or on a set of six indices of diversity selected from the most commonly used. We showed that actual proportions were the most efficient in cattle but not in lambs, and that discriminant analyses based on six indices of diversity or based on actual proportions of species ranked in decreasing order yielded very similar results in both host communities. We rejected the use of one single index for evaluating diversity in all cases and proposed the following procedure: actual proportions of species provide information on interactions between species and, when there is limited or no interaction, a combination of diversity indices or single indices could be used for estimating diversity. When interactions between species have to be taken into account, the best information will be obtained either from species proportions arranged in decreasing order or a combination of biodiversity indices.

Resistência anti-helmintica em rebanhos caprinos no Estado do Ceará / Anthelmintic resistance in goat herds in the State of Ceará

Um levantamento em nível de campo sobre resistência anti-helmíntica em nematódeos gastrintestinais de caprinos foi realizado em 34 rebanhos no Estado do Ceará. Em cada rebanho foram separados 30 cabritos, de ambos os sexos, com idade variando de 1 a 6 meses, os quais foram individualmente pesados, identificados e distribuídos em três tratamentos: 1) Oxfendazole na dose de 4,75mg/kg; 2) Levamisole na dose de 7,5 mg/kg e 3) Controle (näo medicado). Os anti-helmínticos foram administrados de acordo com o peso individual de cada animal e, a dosagem utilizada para cada produto foi a recomendada pelo laboratório fabricante. Foram colhidas fezes dos animais de todos os tratamentos, para OPG e coprocultura, no dia da medicaçäo e 7 dias após. Dos 34 rebanhos avaliados, 7 (20,6 por cento) apresentaram resistência aos imidazóis, 6 (17,6 por cento) aos benzimidazóis e 12 (35,3 por cento) revelaram resistência múltipla. Apenas em 9 rebanhos (26,5 por cento), os nematódeos foram sensíveis aos anti-helmínticos avaliados. Através do questionário aplicado detectou-se que 52,9 por cento dos caprinocultores entrevistados usavam anti-helmínticos de amplo espectro. Os resultados das coproculturas mostraram que os gêneros sobreviventes à medicaçäo com oxfendazole foram principalmente Haemonchus sp, seguido em menor frequência por Oesophagostomum sp, enquanto que ao cloridrato de levamisole sobreviveram Haemonchus sp, Oesophagostomum sp e Trichostrongylus sp

Analysis of first gastric compartment fluid collected via percutaneous paracentesis from healthy llamas.

OBJECTIVE: To evaluate the safety and efficacy of percutaneous paracentesis for fluid collection from the first gastric compartment of healthy llamas and to describe characteristics of that fluid. DESIGN: Prospective study. ANIMALS: 10 healthy adult llamas. PROCEDURE: Physical examinations were performed prior to sample collection and for 14 days afterwards. A CBC was performed prior to sample collection and 5 days later. A 16-gauge, 7.5-cm stainless steel needle, positioned approximately 20 cm caudal to the costochondral junction of the last rib, was pointed in a dorsocraniomedial direction and pushed through the abdominal wall into the lumen of the first gastric compartment. Fluid was aspirated and analyzed immediately for color, odor, consistency, pH, methylene blue reduction (MBR) time, protozoa, and bacteria. RESULTS: Fluid samples were obtained from 9 of 10 llamas. Mean volume was 4.1 ml, mean pH was 6.67, and mean MBR time was 173 seconds. Odor was slightly acidic, color was light brown-green to light yellow-green, and consistency was moderate. Small protozoa with variable iodine staining and gram-negative bacteria were commonly detected. With few exceptions, results of physical examinations and CBC remained within reference ranges. CLINICAL IMPLICATIONS: Fluid samples from the first gastric compartment can be successfully obtained by percutaneous paracentesis. Fluid characteristics were similar to those of fluid collected via orogastric tube in llamas and cattle.

Parasitic gastritis in a llama (Lama glama) associated with inhibited larval Teladorsagia spp. (Nematoda: Trichostrongyloidea).

A 7-year-old female llama was experimentally infected with 500 Fasciola hepatica metacercariae then turned out onto pasture also grazed by domestic sheep. The llama was necropsied approximately 22 weeks post infection. Routine examination of the gastrointestinal tract revealed diffusely coalescing, umbilicated nodules covering the caudal one-fifth of the third stomach compartment. Microscopically, the mucosa was irregularly thickened. Numerous nematode larvae were present in glandular lumens, often extending to the base of the glands. Where nematodes were most numerous, decreased numbers of parietal cells, attenuation of glandular epithelium and increased collagen within the lamina propria were evident. Of a total of 6510 adult nematodes in the third stomach compartment, 51% were Teladorsagia spp., 47% were Trichostrongylus axei, and 2% were Camelostrongylus mentulatus. Except for C. mentulatus, three sheep that had grazed with the llama and were necropsied at approximately the same time, harbored the same nematode species. The total number of larvae in the llama was 56,710, with more than 97% being ostertagiine early fourth-stage larvae. Ostertagiine larvae were also present in the sheep. Based on the composition of the adult populations in the llama and sheep, the larvae were considered to be species of Teladorsagia. Additionally, the larger numbers of early fourth-stage larvae indicated that the development of Teladorsagia spp. in the llama is inhibited.

The pathogenesis of experimental Haemonchus longistipes infection in camels.

The pathogenesis and clinical signs of Haemonchus longistipes infection were studied in four experimentally infected camels two of which were adults and the other two were young. In the former animals, an acute infection developed, characterized by mucoid diarrhoea, anorexia, anaemia, loss of body weight, oedema of the lower parts of the limbs, general malaise and death at 8-10 weeks post-infection. In the two younger camels, a less dramatic disease was encountered with less severe symptoms and no oedema, but also terminating fatally at 19-20 weeks post-infection. Parasitological, haematological and biochemical parameters were determined during the course of the infection and were mostly comparable with those usually encountered in haemonchosis of other animals.

Haemonchus contortus third stage larvae in sheep: kinetics of arrival into the abomasum and transformation during rumino-omasal transit.

The kinetics of passage of Haemonchus contortus third stage larvae through the omasoabomasal orifice were analysed in sheep for six hours after their administration by the nasooesophageal route. The larvae moved into the abomasum more slowly than the liquid phase of the ruminal contents. They arrived in three different forms: sheathed, exsheathed or coiled. A very small number of exsheathed larvae seemed to be necessary for inducing early modifications in permeability of the abomasal mucosa.

[Immune response in sheep experimentally infected with Haemonchus contortus, Comparative study in male and female (author's transl)]. / Réponse immunitaire chez les ovins infestés expérimentalement par Haemonchus contortus. Etude comparative chez le mále et chez la femelle.

Merino breed sheep eight months old at the beginning of the experiment and carriers of hemaglobin A were used. They were infected one or more times with H. contortus larvae and then challenged with 500 or 5000 larvae L3. Self-cure was reproduced and animals were found immune after infectation. Self-cure was more evident in females than in males and immunity was also better and appeared earlier in females than in males.

[Validity of the two species O. lienalis and O. gutturosa from bovines (author's transl)]. / Validité des deux espèces Onchocerca lienalis et O. gutturosa, chez les bovins.

A new morphological analysis of the Onchocerca from the gastrosplenic ligament reveals characteristics confirming the validity of the species O. lienalis as distinct from the cervical Onchocerca, O. gutturosa. The dermic microfilaire of the two species have completely different distributions: the microfilariae of O. gutturosa are gathered in the cephalic region of Bovines while that of O. lienalis can be found in the umbilical region. Therefore we suspect strongly that the life cycle evolving in S. ornatum in England is that of O. lienalis and not of O. gutturosa as previously postulated; and we think that O. gutturosa is more likely to evolve in Culicoides than in Simulium.