The effect of age of host in resistance expressed at the gut level in rats infected with Fasciola hepatica

The development of oral and intraperitoneal infections with Fasciola hepatica in young and old rats showed that the gut was involved in the expression of age resistance. The role of the gut was assessed by comparison of the number of flukes recovered 4 and 10 weeks after oral or intraperitoneal infection of 2-, 6-, 15-, and 35-week-old male Wistar rats and 6- and 15-week-old male DA rats with encysted metacarcariae of F. hepatica.Rats of both strains behaved similarly in their response to F. hepatica infection. For both routes of infection the number of flukes recovered decreased as host age increased. In 22- and 6-week-old rats equal numbers of flukes were recovered at 4 and 10 weeks after oral or intraperitoneal infection. In 15-week-old rats, fluke burdens 4 weeks after infection were significantly greater following intraperitoneal infection than oral infection. A significant loss of flukes from the intraperitoneal infection of 15-week-old Wistar rats occured between 4 and 10 weeks after infection. In 35-week-old Wistar rats there was no significant effect for route or age of infection.As intraperitoneal infection (to by-pass rejection at the gut level) only partially eliminates the age response, additional age related mechanism(s), able to reject flukes at some time after they have entered the peritoneal cavity, must be operative in the peritoneal cavity and/or the liver.     

Fenbendazole for treatment of Paragonimus kellicotti infection in dogs.

The effect of fenbendazole therapy was studied in 9 dogs with pulmonary paragonimiasis induced by inoculation of metacercariae (25/dog) of Paragonimus kellicotti. At 42 to 47 days after 6 dogs were inoculated, they were given fenbendazole in 2 divided doses totaling 50 mg (4 dogs) or 100 mg (2 dogs)/kg of body weight each day for 10 to 14 days. Three dogs were not treated. The passage of Paragonimus eggs in the feces ceased after 3 days at the high dosage and after 3 to 8 days at the low dosage. All dogs were euthanatized and necropsied on day 14. Live flukes were not recovered from the lungs of any treated dog, but 15, 19, and 23 live flukes were recovered from the untreated dogs.     

Pathogenesis of canine parvovirus enteritis: sequential virus distribution and passive immunization studies

After oral inoculation, the sequential distribution of canine parvovirus was studied in 14 nine-week-old seronegative beagle dogs. Two or three dogs were necropsied on days 1 through 6 after inoculation. Tissues were collected for virus isolation, immunofluorescence testing, and light microscopy. Virus was isolated from, and fluorescent cells were seen in the tonsil, retropharyngeal and mesenteric lymph nodes one and two days after inoculation. Virus infection of systemic and intestinal lymphoid tissues occurred as early as three days after inoculation and was associated with viremia. Intestinal epithelial infection was first seen four days after oral inoculation. All dogs were viremic before intestinal epithelial infection was found. Fecal virus excretion first occurred four days after oral virus inoculation. Intestinal virus infection and lesions became progressively more severe between four and six days after inoculation. The severity of intestinal lesions was variable and related to the severity of systemic lymphoid tissue lesions and the magnitude and duration of viremia. Four littermates of virus-infected dogs were passively immunized against canine parvovirus with convalescent canine serum 24 hours after oral virus inoculation. Neither clinical signs, lymphopenia, nor fecal virus excretion occurred in passively immunized dogs. Intestinal epithelial infection was not demonstrable by immunofluorescence testing when passively immunized dogs were necropsied four, five, and six days after virus inoculation.     

Efficacy of clorsulon against Fascioloides magna infection in sheep

In a study to evaluate the efficacy of clorsulon against Fascioloides magna infection in sheep, 12 ewes were inoculated orally with 100 metacercariae of F magna, and 6 were treated with clorsulon (15 mg/kg of body weight) 8 weeks after inoculation. The sheep were euthanatized 16 weeks after inoculation, flukes were recovered, and the liver and other tissues were subjectively scored for the severity of lesions (0 to 4+). The number of flukes recovered from the clorsulon-treated group (3.8 +/- 1.2 flukes) was significantly (P = 0.025) lower than the number of flukes recovered from the group of untreated controls (10.0 +/- 6.6 flukes). The severity of lesions was significantly (P = 0.004) reduced (45.9%) in the treated group (2.0 +/- 1.1), compared with that in the untreated controls (3.7 +/- 0.5). In the untreated group, 3 sheep died and 1 became moribund 14 to 16 weeks after inoculation. The data suggested that a single treatment with clorsulon at a dosage of 15 mg/kg 8 weeks after inoculation was not effective in preventing F magna infection in sheep, because the survival of only a few F magna is potentially fatal in sheep within 6 months after infection.     

Experimental toxoplasmosis in buffalo calves

Eight buffalo calves were inoculated with infectious oocysts of a virulent strain of Toxoplasma gondii, five with 1 × 10⁵, and the other three with 5 × 10⁵ oocysts each while two more were kept as non-inoculated controls. Infected animals developed pyrexia, anorexia, conjunctivitis and dyspnoea. The clinical symptoms, haematological changes and serological response were of a low order. The appearance of haemagglutinating antibodies at significant levels (? 1:64) was first observed at 21 days after inoculation (DAI), peaked at 42 DAI and rapidly declined after 63 DAI. The inoculated calves were killed (or died) at intervals from 11 DAI to 110 DAI. The organism could be recovered from several times of a calf that died 11 DAI, but was rapidly removed subsequently. Only the lymph nodes were infective till 32 DAI. Parasitism of the retina was demonstrated in one calf. The significance of these findings is discussed.     

CORYNEBACTERIUM PSEUDOTUBERCULOSIS INFECTION OF SHEEP: ROLE OF SKIN LESIONS AND DIPPING FLUIDS

Caseous lymphadenitis (CLA) infection was established experimentally in a total of 30, 2-tooth merino wethers. In the first experiment a broth culture of the causative organism, Corynebacterum pseudotuberculosis was placed directly on to a freshly shorn area on the right shoulder of 21 sheep after pretreatment with a defatting agent, water or 4 different commercial sheep dips. Within 6–13 days focal skin lesions appeared on 7 sheep and these were followed by abscessation of the right prescapular lymph node. Lung lesions of CLA developed in 6 sheep; 5 of which had skin lesions. In the second experiment C. Pseudotuberculosis broth culture was applied over the right shoulder region of 14 sheep, 24 hours post shearing. The 7 animals had only 1 application of the culture and the remaining 7 had 4 applications on consecutive days. A total of 9 of the 14 sheep developed skin lesions and subsequent CLA in the right prescapular lymph nod but there was no significant difference between the 2 methods of application. As part of the second experiment a broth culture of C. pseudotuberculosis was added to a commercial arsenical sheep dip and 2 hours later sprayed on to the right side of sheep shorn 24 hours or 2 weeks previously. Within 6–13 days all 14 sheep treated in this way developed skin lesions from which C. pseudotuberculiosis was recovered in dense pure growth. Healing time of skin lesions in all affected sheep ranged from 17–72 days post inoculation. A serological test to detect the presence of C. pseudotuberculosis antitoxin was used at regular intervals on all experimental sheep. The earliest positive reaction in an affected sheep was recorded 4 weeks post inoculation. In 23 known affected sheep tested at 35 weeks post inoculation, 10 were positive to the Zaki test. No false positive reactors were recorded. The localisation of focal lung lesions in the interstitial tissue suggests that pulmonary abscessation caused by C. pseudotuberculosis develops via the haematogenous route.     

卫氏与斯氏并殖吸虫在实验动物体内分布的比较观察

目的 比较两种主要对人体致病的肺吸虫在实验动物肺内与肺外（胸、腹腔）的分布，为临床诊断及药物治疗提供参考。方法 粪检肺吸虫卵阴性的猫犬分别经口感染卫氏并殖吸虫（P．W）与斯氏并殖吸虫（P．S）囊蚴，饲养3个月后粪检肺吸虫卵阳性时对犬、猫进行解剖，观察与统计内肺外虫数。结果 猫犬解剖所获得P．W与P．S成虫均以左、右肺下叶寄生成虫数最多，猫、犬感染P．W后检获肺外期与左、右肺的童虫数均无显著性差异（P〉0．05）。猫感染P．S后所检获肺外期童虫数与左、右肺的童虫数有显著性差异（P〈0．05），而犬感染P．S所检获肺外期童虫数与左、右肺的童虫数有高度显著性差异（P〈0．01）。猫感染P．W与P．S囊蚴后虫体平均回收率为41．84％，39．85％；犬感染P．w与P．S囊蚴后虫体平均回收率分别为47．44％，24．57％。经统计学处理猫感染两种虫体回收率显著高于犬（P〈0．05）。结论 两种肺吸虫在实验动物犬、猫肺部的分布均以左、右肺下叶寄生成虫数最多，猫犬感染P．S所检获的肺外期童虫数与检获左、右肺内的童虫数分别为有显著性差异（P〈0．05）与高度显著性差异（P〈0．01），猫感染虫体的回收率明显高于犬。     

Experimental infection with the small intestinal trematode,Haplorchis pumilio,in young dogs

Fishborne zoonotic trematodes (FZT) are highly prevalent in Southeast Asia. Recent studies on the role of domestic animals in the transmission of FZT in Northern Vietnam found that dogs, mainly infected with Haplorchis pumilio, contributed widely to the transmission of FZT. On this background, we conducted an experimental infection with H. pumilio to elucidate population dynamics and host reactions in dogs. Eight household-reared dogs (3–6 months old), were each orally infected with 500 H. pumilio metacercariae obtained by artificial digestion of naturally infected fish. Another eight dogs were included as uninfected controls. Faecal examination for eggs was performed twice weekly using a sieving and sedimentation technique. Body temperature and weight of the dogs were measured as was total white blood cells, blood eosinophils and packed cell volume. Subsets of dogs were examined post-mortem for presence of adult FZT at three different time points post infection by sectioning of the small intestine and caecum into four parts. Patent infections established in all eight infected dogs. The worm establishment ranged from 15 to 121 flukes (3–24%, mean 12%). Faecal egg excretion was measured in all eight infected dogs but no more than two eggs per g faeces (epg) were found at any time. Infections lasted for at least two months as documented by the presence of adult flukes in all three dogs necropsied on day 58 post infection. The predilection site of the flukes was identified as the lower part of jejunum (93% of total worm burden). The results of the haematological tests did not differ between the infected and uninfected group. Further, no clinical symptoms were observed in the infected group and no macroscopic pathological changes could be assigned to the trematode infections, neither did histopathological examination of the intestine reveal any differences between the infected and the control dogs. This study provides the first basic knowledge on the establishment, duration and location of H. pumilio infection in dogs. However, before any control measures can be recommended, knowledge regarding infection dynamics, epidemiology, health impact and control is needed.     

The effects of Eimeria acervulina infection on the metabolism of chick duodenal tissue

Broiler chicks, 2--3 weeks old were infected with eimeria acervulina, and the metabolism and ultrastructure of the infected duodenal tissue were studied during the period 3--14 days after inoculation (DAI). Between 4 and 5 DAI duodenal rings showed an increase in C-1/C-6 ratios of CO2 evolved from glucose as well as decreases in the rates of oxidation of glucose and octanoic acid. Between 4--7 DAI mitochondria from infected epithelial layers had reduced rates of octanoic acid and alpha-ketoglutaric acid oxidation as compared to controls. Electron microscopic observations confirmed the biochemical findings. At 5--6 DAI mitochondria in many uninfected cells were progressively swollen and then vacuolated as the cristae appeared to break down. Mitochondria in cells which contained parasites did not show these changes.     

The establishment and development of Haemonchus contortus in goats

Twelve goats were inoculated with 40,000 third-stage Haemonchus contortus larvae and two were killed on each of Days 4, 7, 11, 14, 18 and 21 after inoculation (DAI). The number of worms that established, and the site of development were recorded. More worms established in the fundic, than in the middle or pyloric thirds of the abomasum. Early development occurred within the mucosa; emergence into the lumen started between 7 and 11 days after infection. By 4 DAI, all worms had completed the third moult to the L4 stage. At 11 DAI the majority of the worms were adults. A mean of 13.2% of the female worms had eggs in their uteri at 18 DAI; by 21 DAI more than half of the female worms had eggs in their uteri. The development of H. contortus was essentially similar to that described in sheep.     

The establishment and development of Trichostrongylus colubriformis in goats

Twelve goats were inoculated with 20,000 infective larvae of Trichostrongylus colubriformis and two were killed on each of Days 4, 7, 11, 14, 18 and 21 after inoculation (DAI). The number of worms that established, and the site of development were recorded. Most of the worms established within the first 3 m of the small intestine. There was little relocation or loss of nematodes after establishment. The worms started to migrate from the mucosa to the lumen 11 days after infection. At 4 DAI, 63% of the worms were still at the late L3 stage; the remainder of the worm population had completed the third moult to the L4 stage. The population at 11 DAI comprised largely young adults. When 21 DAI was reached, about 57% of the female worms had eggs in their uteri.     

Dynamics of viral spread in bluetongue virus infected calves

The kinetics of viremia and sites of viral replication in bluetongue virus (BTV) infected calves were characterized by virus isolation, serology and immunofluorescence staining procedures. In addition, the role of the regional lymph node and lymphatics draining inoculated skin in the pathogenesis of BTV infection was determined by analyzing efferent lymph collected from indwelling cannulas. Viremia persisted for 35 to 42 days after inoculation (DAI) and virus co-circulated with neutralizing antibodies for 23 to 26 days. Virus was first isolated from peripheral blood mononuclear (PBM) cells at 3 DAI, after stimulation of PBM cells with interleukin 2 and mitogen. BTV was frequently isolated from erythrocytes, platelets and stimulated PBM cells but never from granulocytes and rarely from plasma during viremia. Virus was consistently isolated from erythrocytes late in the course of veremia. Interruption of efferent lymph flow by cannulation delayed the onset of viremia to 7 DAI. BTV was infrequently isolated from lymph cells, and few fluorescence positive cells were observed after lymph and PBM cells were labelled with a BTV-specific monoclonal antibody. Virus was isolated from spleen by 4 DAI and most tissues by 6 DAI, whereas virus was isolated from bone marrow only at 10 DAI. Virus was not isolated from any tissue after termination of viremia. It is concluded that primary viral replication occurred in the local lymph node and BTV then was transported in low titer to secondary sites of replication via infected lymph and PBM cells. We speculate that virus replication in spleen resulted in release of virus into the circulation and non-selective infection of blood cells which disseminated BTV to other tissues. Virus association with erythrocytes likely was responsible for prolonged viremia, although infected erythrocytes eventually were cleared from the circulation and persistent BTV infection of calves did not occur.     

Canine parvovirus enteritis 1: Clinical, haematological and pathological features of experimental infection

The effect of oral infection of puppies, eight and 10 weeks old, with canine parvovirus of faecal origin was studied. Clinical signs of enteric disease were first apparent at five days after inoculation and persisted during days 6 and 7 after inoculation. The severity of clinical signs varied from transient dullness and anorexia to emesis, dysentery and death. Changes in haematological parameters were first found at day 3 after inoculation when a relative lymphopenia was observed. A profound neutropenia developed in severely affected dogs after the appearance of clinical enteric disease. Post mortem examination revealed thymic atrophy in all dogs killed on day 4 after inoculation. Macroscopic changes in the small intestine were apparent only in animals examined during the phase of severe enteric disease and consisted of thickening, rigidity and congestion of the small intestines. Microscopically there was lymphocytolysis in the thymic cortex and the germinal centres of the lymph nodes from days 2 and 3 after inoculation respectively and this rapidly resulted in depletion of these tissues. There was repopulation of lymph nodes from day 7 after inoculation but significant thymic regeneration was not apparent during the course of this study. In the small intestine, necrosis of crypt epithelium, atrophy of villi and, in some areas, complete collapse of mucosal architecture were found but the extent of these changes varied along the length of the small intestine and between individuals. Regenerative intestinal changes were observed in those animals surviving the acute phase of enteric dysfunction. The variable severity of clinical and enteric lesions, together with the factors which may affect the expression of clinical disease, are discussed.     

Pathophysiologic effects of experimentally induced Fascioloides magna infection in sheep

The pathophysiologic responses of 13 sheep inoculated orally with 100 metacercariae of Fascioloides magna were monitored for 4 months after inoculation. There were no differences in weight gains between these and a number of noninoculated control sheep throughout the experiment. Complete blood cell counts showed an increase only in the absolute number of eosinophils. Serum preparations (2 times a week) from 7 inoculated and 7 noninoculated sheep did not identify any significant changes in alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transferase activities. There were no changes in total bilirubin, BUN, creatinine, inorganic phosphorus, calcium, albumin, chloride, potassium, and sodium values. Four months after they were inoculated, all sheep were necropsied, and flukes were recovered. Gross lesions attributed to fluke migration were found in the liver and portal lymph nodes, diaphragm, lungs, kidneys, and spleen. Microscopically, liver lesions in inoculated sheep occurred in the portal areas, veins, and Glisson's capsule and were characterized by both active and chronic forms of inflammation. Abundant infiltrates of eosinophils and plasma cells often marked the portal areas. Endophlebitis, with or without thrombosis, was the predominate vascular lesion. The flukes recovered varied greatly in size (6.5 to 48.0-mm long) and demonstrated some sexual development, but none was sexually mature.     

Hematology and clinical pathology of experimental Fascioloides magna infection in cattle and guinea pigs.

The hematologic and clinico-pathologic response to Fascioloides magna infection in cattle and guinea pigs was investigated. Twelve calves (six infected and six controls) were monitored for 26 weeks after inoculation with 1000 metacercariae. All calves remained healthy and there were no significant differences in weight gains between infected and control groups. Flukes (mean = 9.2, range 1–32) were recovered from the liver and abdominal cavity of all infected calves. The only significant response observed in the complete blood counts was an eosinophilia present in the infected calves extending from Weeks 2 to 26 post-infection. There were no significant differences in serum levels of aspartate aminotransferase and only minor increases in the levels of gamma-glutamyl transferase and sorbitol dehydrogenase.

A total of 48 infected and 48 control guinea pigs from three separate experiments were monitored for 16 weeks after inoculation with 20 metacercariae of Fascioloides magna. Infected guinea pigs died between 7 and 114 days after infection, and flukes (ean = 2.5, range 0–13) were recovered from the liver, abdominal cavity, lungs, thoracic cavity, skeletal muscle and subcutaneous tissue. There were no differences in weight gains between infected and control guinea pigs. Complete blood counts showed increases in white blood cell, monocyte and neutrophil counts from between the third and fourteenth weeks post-infection; however, the differences were not consistently significant. Infected guinea pigs developed a significant eosinophilia and basophilia from 2 to 16 weeks post-infection. There were no significant changes in the serum levels of alanine aminotransferase or gamma-glutamyl transferase. There was an increase in the serum levels of aspartate aminotransferase beginning at 5 weeks post-infection. The response observed in the guinea pigs was similar to that reported in sheep, suggesting the suitability of the guinea pig as a model for Fascioloides magna infection in the sheep.     

Experimental Final Hosts of Metagonimus Hakubaensis (Trematoda: Heterophyidae) and Their Suitability to the Fluke

Seven laboratory mammal and bird species were orally inoculated with 200–1,000 encysted Metagonimus hakubaensis metacercariae that had been isolated from naturally infected lampreys (Lethenteron reissneri) captured in Aomori Prefecture. At 8 and 15 days post-infection, adult flukes were recovered from all of the laboratory animals tested, and therefore, hamster, rat, mouse, dog, cat, chicken and quail were considered as final hosts of M. hakubaensis. Recovery rates of the fluke were higher in dogs and hamsters than in cats, rats, mice, chickens and quails. The flukes recovered from dogs and hamsters showed increased body length and higher fecundity than those recovered from the other hosts. These results indicate that the suitability of dogs and hamsters for M. hakubaensis infection is higher than that of the other laboratory animals.     

Development of villus atrophy in the small intestine of sheep infected with Trichostrongylus rugatus

Pairs of sheep infected with 120 000 larvae of Trichostrongylus rugatus were killed at intervals from 2 to 56 days after infection (DAI). Worms were located in tunnels in the epithelium of villi or upper intestinal crypts at all stages of development. Villus atrophy developed progressively until 16 DAI, when surface microtopography, characterised by subtotal villus atrophy, stabilised. Most severe lesions were in the first 3 m of small intestine where the density of nematodes was highest. Discontinuities in the epithelium and effusion of inflammatory cells and tissue fluids into the lumen were rare. No effects of infection on body-weight gain, appetite or serum total protein and albumin were evident in the first 20 days of infection. However, it was concluded that T. rugatus fundamentally resembled T. colubriformis and T. vitrinus in the response it elicited in the intestine of sheep, and must be considered potentially pathogenic.     

Morphogenesis of Trichostrongylus rugatus and distribution during development in sheep

Morphogenesis of Trichostrongylus rugatus was examined in 16 sheep experimentally-infected with 120 000 third-stage larvae and killed 2, 4, 6, 8, 10, 12, 16 and 20 days later (DAI). Third stage larvae moulted between Days 4 and 6, and fourth stage larvae moulted on Day 10 after infection. Four sheep first passed eggs in the faeces between Days 16 and 18 after infection. Rate of growth of larvae was constant between 2 and 10 DAI followed by a period of rapid growth from 10 to 16 DAI. Major features of larval development are described. Nematodes were largely restricted to the first 6 m of gut with 71% of worms occurring in the first 3 m.     

Onset of immunity with Mycoplasma synoviae: comparison of the live attenuated vaccine MS-H (Vaxsafe MS) with its wild-type parent strain (86079/7NS)

The onset of protective immunity with MS-H was determined through experimental challenge and compared with the parent strain 86079/7NS. MS-H vaccinates and 86079/7NS inoculates were challenged at 1, 2, 3, 4, 5, and 6 wk after vaccination, then examined 2 wk after challenge for signs of respiratory disease. Serologic results indicated that 100% of MS-H vaccinates had antibodies to MS by 3 wk after vaccination and 100% of 86079/7NS inoculates were positive by 2 wk after inoculation. From 3 wk after vaccination, MS-H vaccinates had a significantly lower incidence of air sac lesions and, from 4 wk after vaccination, a significantly lower air sac lesion severity. In 86079/7NS-inoculated birds, a significantly lower incidence of air sac lesions was observed from 1 wk after inoculation, and air sac lesion severity was significantly lower than the unvaccinated controls at 3 wk after inoculation. It would appear that, under the conditions of this experiment, protective immunity elicited by MS-H appeared at 4 wk after vaccination, slightly later than the appearance of serum antibody. Although the MS-H vaccine was slower to establish protective immunity than 86079/7NS, there was no significant difference between the two strains by 4 wk after vaccination or inoculation.     

PREVALENCE OF COMPUTED TOMOGRAPHIC SUBCHONDRAL BONE LESIONS IN THE SCAPULOHUMERAL JOINT OF 32 IMMATURE DOGS WITH THORACIC LIMB LAMENESS

Osteochondrosis is a common developmental abnormality affecting the subchondral bone of immature, large breed dogs. The purpose of this retrospective study was to describe CT lesions detected in scapulohumeral joints of 32 immature dogs undergoing CT for thoracic limb lameness. Eight dogs (14 scapulohumeral joints) had arthroscopy following imaging. Thirteen dogs (19 scapulohumeral joints) were found to have CT lesions, including 10 dogs (16 scapulohumeral joints) with subchondral bone lesions and 3 dogs with enthesopathy of the supraspinatus tendon. In one dog, subchondral bone lesions appeared as large oval defects within the mid‐aspect of the glenoid cavities, bilaterally. These lesions resembled osseous cyst‐like lesions commonly identified in the horse. This is the first report of such a presentation of a subchondral bone lesion in the glenoid cavity of a dog. In all dogs, small, focal, round or linear lucent defects were visible within the cortical bone at the junction of the greater tubercle and intertubercular groove. These structures were thought to represent vascular channels. Findings from this study support the use of CT as an adjunct modality for the identification and characterization of scapulohumeral subchondral bone lesions in immature dogs with thoracic limb lameness.