Ecological basis of parasite control: Trematodes with special reference to fascioliasis

In this paper the main ecological components of selected animal trematode infection cycles are considered with regard to the possibilities of control. The geographical distributions of Fasciola hepatica, F. gigantica, Paramphistomum microbothrium, Schistosoma bovis and S. mattheei are compared in relation to the distribution patterns of their snail intermediate hosts. In order to constitute an effective lifecycle host, intermediate host and the eggs and freeliving stages of the parasite overlap in the effective biotope. Comparing the biotopes of the different trematodiases it becomes evident that they have much in common particularly as the snail intermediate hosts occupy identical niches in a food-chain in which the pollution by the host species results in abundant food for the snail. Moreover, the physical activaties of herbivores, e.g. trampling down the turf, create favourable habitats for the intermediate host.The dynamic nature of the freshwater snail habitats characteristic for trematodiasis, regularly results in a complete disappearance of the effective biotopes in the field. With regard to the parasite these effects are overcome by a long life-expectancy of egg producing parasites in the host population. Small scale changes in availability of appropriate hosts for successful cercarial establishment are compensated by the extended period of cercarial shedding from the snail population.These features in combination with the survival of eggs and the grazing and drinking behaviour characteristics of the hosts tend to stabilize the potential oscillations in transmission rate. Because of the complicated nature of interdependency within the host-trematode-intermediate host complex, the ecological base with regard to practical measures is fundamentally wide. However, the pressure upon the situation by social and economic conditions limits operative possibilities considerably.     

Host stress physiology and Trypanosoma haemoparasite infection influence innate immunity in the woylie (Bettongia penicillata)

Understanding immune function is critical to conserving wildlife in view of infectious disease threats, particularly in threatened species vulnerable to stress, immunocompromise and infection. However, few studies examine stress, immune function and infection in wildlife. We used a flow cytometry protocol developed for human infants to assess phagocytosis, a key component of innate immunity, in a critically endangered marsupial, the woylie (Bettongia penicillata). The effects of stress physiology and Trypanosoma infection on phagocytosis were investigated. Blood and faecal samples were collected from woylies in a captive facility over three months. Trypanosoma status was determined using PCR. Faecal cortisol metabolites (FCM) were quantified by enzyme-immunoassay. Mean phagocytosis measured was >90%. An interaction between sex and FCM influenced the percentage of phagocytosing leukocytes, possibly reflecting the influence of sex hormones and glucocorticoids. An interaction between Trypanosoma status and FCM influenced phagocytosis index, suggesting that stress physiology and infection status influence innate immunity.     

Experimental infection of the Guyanese zebu with Trypanosoma vivax

The Guyanese strain of Trypanosoma vivax is pathogenic for the local Brahman zebu; the experimental infection of 19 one-year old cattle was followed by a moderate and transitory fever, a drop in packed cell volume (PCV) and a quick and marked weight loss of 10 to 17 kg one month after as compared to the 16 non-infected animals. Other symptoms were associated with the parasitaemia: diarrhoea, swollen haematic glands on the neck and the flank, lachrymation, weakness. Despite a trypanocidal treatment injected one month post-infection, one animal died and the weight losses of others were not compensated for three months later. The particular susceptibility of weaning animals is discussed as well as its implications in the control of trypanosomosis.     

Degenerative joint disease (osteoarthrosis): A review with special reference to the dog

Nomenclature, incidence, etiology, pathogenesis and morphological appearance of primary and secondary osteoarthrosis (osteoarthritis) are discussed. Differences and similarities between osteoarthrosis in man and the dog are mentioned. Primary osteoarthrosis occurs in the dog but secondary osteoarthrosis seems to be more frequent. In the dog hip dysplasia, Legg-Perthes' disease, osteochondritis dissecans of the shoulder and ununited anconeal process are conditions which, among others, give rise to osteoarthrosis. Changes in the knee caused by instability after rupture of the cruciate ligaments are not those of true osteoarthrosis. There is only minimal involvement of the joint cartilage in spite of osteophyte formation, thickening of the synovium and derangement of the menisci. Clinical signs in degenerative joint disease are usually insidious in onset. For a varying period of time they are as a rule not very conspicuous. In more advanced cases the cljnical manifestations are pain, limitation of movement and muscle atrophy. The underlying changes are cartilage destruction, subchondral sclerosis, osteophytes and thickening of the synovium. In very advanced cases in man there is even attrition of bone, which clinically leads to instability and subluxation. In human coxarthrosis cyst formations are frequently seen. Etiology and pathogenesis are obscure, or only partly understood, and in animals diagnosis is sometimes difficult. There is often poor correlation between severity of radiographic changes and clinical signs. Résumé. On examine la nomenclature, l'incidence, l'étiologie, la pathogénie et l'aspect morphologique de l'ostéo-arthrose (ostéo-arthrite) primaire et secondaire. On mentionne les différences et similitudes entre I'ostéo-arthrose rencontrée chez l'homme et chez le chien. L'ostéo-arthrose primaire se rencontre chez le chien, mais les cas d'ostéo-arthrose secondaire sont plus fréquents. Chez le chien, la dysplasie de la hanche, la maladie de Legg-Perthes, l'ostéochondrite disséquante de l'épaule et I'apophyse anconée disloquée sont des états qui, entre autres, engendrent l'ostéo-arthrose. Des transformations du genou, causées par une instabilité après rupture des ligaments croisés, ne sont pas celles de I'ostéo-arthrose proprement dite. Le rôle du cartilage articulaire n'est que minime, malgré l'apparition d'ostéophytes, l'épaississement des membranes synoviales et les troubles des ménisqua. Les signes cliniques des maladies articulaires dégéntratives sont généralement insidieux au départ. Pendant une période de temps variable, ils ne sont d'ordinaire pas très marqués. Pour les cas plus graves, les manifestations cliniques sont la douleur, la restriction des mouvements et l'atrophie musculaire. Les transformations qui sont à base de ces manifestations comprennent: destruction du cartilage, sclérose sous-cartilagineuse, ostéophytes et épaississement des membranes synoviales. Si chez l'homme, l'etat est très grave, on assiste même à l'attrition des os, qui, du point de vue clinique, mène à I'instabilité et la subluxation. En cas de coxarthrose chez l'homme, on observe fréquemment la formation de kystes. On ne connaît pas bien et ne comprend que partiellement l'étiologie et la pathogénie de ces maladies et, chez les animaux, le diagnostic est beaucoup plus difficile à établir. Très souvent on n'obtient pas de bonne corrélation entre I'importance des changements radiographiques et les signes cliniques. Zusammenfassung. Nomenklatur, Häufigkeit, Ätiologie, Pathogenese und morphologisches Aussehen von primärer und sekundärer Osteoarthrosis (Osteoarthritis) werden besprochen. Unterschiede und Ähnlichkeiten zwischen Osteoarthrosis des Menschen und des Hundes werden erwähnt. Primäre Osteoarthrosis tritt beim Hund auf, jedoch scheint die sekundäre Osteoarthrosis häufiger zu sein. Beim Hund sind Hüftendysplasie, Legg-Perthessche Krankheit, Osteochondritis dissecans der Schulter und unvereinigte anconeale Prozesse Zustände, die unter anderem zu Osteoarthrosis führen. Verändemngen am Knie, die durch Instabilität nach Ruptur der Kreuzbänder verursacht werden, sind nicht die echter Osteoarthrosis. Der Gelenkknorpel ist nur minimal betroffen, trotz Osteophytenbildung, Verdickung der Synovia und Meniskusverlagerung. Klinische Zeichen degenerativer Gelenkerkrankungen sind gewöhnlich anfangs mehrdeutig. In der Regel sind sie unterschiedlich lange nicht sehr auffällig. In fortgeschritteneren Fällen sind die klinischen Merkmale Schmerz, Bewegungsbehinderung und Muskelatrophie. Die zugrundeliegenden Veränderungen sind Knorpelzerstörung, subchondrale Sklerose, Osteophyten und eine Verdickung der Synovia. In sehr fortgeschrittenen Fällen beim Menschen tritt selbst Knochenabnutzung auf, die klinisch zu Instabilität und Subluxation führt. Bei Coxarthrosis des Menschen wird häufig Zystenbildung beobachtet. Ätiologie und Pathogenese sind dunkel oder nur teilweise aufgeklärt, und bei Tieren ist die Diagnose viel schwieriger. Oft besteht eine schlechte Korrelation zwischen der Schwere der radiographischen Verändemngen und den klinischen Zeichen.     

Pathological changes in male genitalia of cattle infected with Trypanosoma vivax and Trypanosoma congolense

Samples for histological studies were taken from the genitalia of 14 bulls (five infected with Trypanosoma vivax, five with T. congolense and four uninfected control animals), slaughtered 12, 22 or 30 weeks post-infection. Infection with Y58 strain of T. vivax and strain 2295 of T. congolense caused various grades of lesions in the male reproductive organs, especially the testes and epididymides. T. congolense produced more severe degenerative changes than T. vivax. It is concluded that in long-standing cases, the result of trypanosome infection is either serious infertility or even sterility.     

Observations on the transmission, immunology, clinical signs and chemotherapy of dourine (Trypanosoma equiperdum infection) in horses, with special reference to cerebro-spinal fluid.

This paper is a record of observations on the transmission and clinical signs of dourine in naturally infected cases of known duration, and of temporal and quantitative aspects of the immune response in blood and cerebro-spinal fluid. Included in the record are observations on the presence of Trypanosoma equiperdum parasites in these body fluids and methods for their detection. There is evidence that the occurrence of nervous symptoms and lesions in infected horses is associated with the presence of Trypanosoma equiperdum parasites in cerebro-spinal fluid. The suitability of cerebro-spinal fluid as an environment for the parasite and its relationship with nervous manifestations of the disease are discussed. Observations support the previously reported lesions of peripheral polyneuritis and suggest a possible correltation between the consitstent position of the nervous lesions and the drainage of cerebro-spinal fluid containing the parasite. Chemotherapy with an experimental drug MSbE was used with varying results in 4 horses at different stages of infection.     

Physiological adaptation to the humid tropics with special reference to the West African Dwarf (WAD) goat

West African Dwarf (WAD) goats are widely distributed in the subhumid and humid zones of Africa but are particularly associated with less favourable environments. Adaptive features such as feeding behaviour, efficiency of feed use and disease tolerance enable WAD goats to thrive on natural resources left untouched by other domestic ruminants. In marginal environments this goat remains the only domestic species that is able to survive. Among its physiological features small body size and low metabolic requirements are important traits that enable the animal to minimize its requirements in area or season where food sources are limited in quality and quantity. Specialized feeding behaviour and an efficient digestive system enable the animal to maximize food intake. Coat colour plays an important role in the evolved adaptation of this goat type. Reproductive fitness as manifested by prolific breeding is a major factor of adaptation. Defence mechanisms against infectious agents enable this type to thrive well in the hot humid tropics. The mechanisms involved in the regulation of these physiological functions of WAD goat are discussed. An understanding of these mechanisms could result in the development of improved techniques for enhancing goat productivity in humid environments.     

Study on the susceptibility of Sahel goats to experimental Trypanosoma vivax infection

Sahel goats, also known as Borno whites are found in the northern semi-arid, tsetse free Sahel region of Nigeria. They are transported alongside cattle from this zone to all other zones in the country, including the tsetse-infested zones, for commercial purposes and are kept for some time in these tsetse-infested zones until they are sold. This study therefore assessed the susceptibility of this breed of goats to trypanosome infection and its response to treatment with Berenil. Six bucks were inoculated intravenously with Trypanosoma vivax through the jugular vein while two served as uninfected control. The mean pre-patent period was 4.5 days and increasing parasitaemia followed the establishment of infection. Onset of parasitaemia was associated with increase in rectal temperature in all the infected goats and the temperature peak coincided with the only parasitaemic peak second week post-infection. The infected goats were treated with Berenil (Hoechst, Germany) 3.5mg/kg body weight at 4 weeks post-infection. The packed cell volume (PCV) continued to fall from a mean 30.73+/-0.01% pre-infection to a mean 13.21+/-0.18% at 1 week post-treatment. Deaths were recorded for 4 of the infected goats 1 week post-treatment while the remaining two died 2 weeks post-treatment, not responding to treatment.     

Response of Trypanosoma vivax and Trypanosoma congolense in zebu cattle in North Cameroon to prophylactic treatment with two formulations of isometamidium

We tested the efficacy of two formulations of isometamidium in a tsetse-infested farm in North Cameroon from 20 August 2000 to 5 January 2001. A total of 90 adult cattle were used in three groups of 30 each corresponding to two treated and one untreated control. Drug efficacies were evaluated in terms of reduction of parasite incidence in the host's blood, maintenance of packed-cell volume (PCV) and weight gains. Both drugs reduced the incidence of parasites even though re-infections 2 weeks after treatment were common. PCV values were similar in both treated groups but higher than in the untreated control. Body weight changes followed a similar trend with the control losing weight from a mean of 427+/-119kg at the beginning to 398+/-93kg in 4 months. Weights increased from 375+/-76 and 396+/-110 to 396+/-69 and 418+/-112kg in the Veridium and Trypamidium groups, respectively. Efficacy was similar between the two formulations of isometamidium in the prophylaxis of bovine trypanosomosis. However, the presence of parasites in some animals barely 2 weeks after treatment suggested that either infections were not cleared or residual drug effects were not sufficient to prevent re-infections.     

Cardiac output technologies with special reference to the horse

Critical illness, anesthesia, primary cardiovascular disease, and exercise may result in marked hemodynamic alterations. Measuring cardiac output (CO) is central to defining these alterations for both clinician and researcher. In the past 10 years, several new methods of measuring CO have been developed for the human medical market. Some of these methods are now validated in the horse and are in clinical use. The Fick method has been used in equine research for more than a century. It depends on simultaneous measurement of mixed venous (pulmonary arterial) and peripheral arterial oxygen content and oxygen uptake by the lungs. The technique is technically demanding, which restricts its clinical use. Indicator dilution techniques, with indocyanine green, cold (thermodilution), or lithium as the marker, have also been widely used in the horse. The indocyanine technique is cumbersome, and thermodilution requires right heart catheterization, which is not a benign procedure, making both of these methods less than ideal for clinical use. Lithium dilution requires catheterization of a peripheral artery and a jugular vein. It has recently been validated in anesthetized adult horses and neonatal foals. Doppler echocardiography is a noninvasive ultrasound-based technique. More accurate measurements are obtained with transesophageal than with transthoracic measurements; however, both methods require considerable technical expertise. Bioimpedance and pulse contour analysis are 2 new methods that have yet to be validated in the horse. With the currently available technology, lithium dilution appears to be the method of measuring CO best suited to the equine clinic.     

Effect of novidium (homidium chloride) chemotherapy on genital lesions induced by Trypanosoma vivax and Trypanosoma congolense infections in Zebu bulls

Zebu bulls chronically infected with Trypanosoma vivax and T. congolense were treated at the 12th week post-infection with novidium and slaughtered at different times after treatment to determine histological evidence of healing of the genital lesions. Though trypanosomes disappeared from the blood soon after chemotherapy, there was incomplete resolution of genital lesions even 10-18 weeks later. Where there is severe degeneration of the testes and epididymes chemotherapy may be ineffective in leading to regeneration and therefore infertility problems may persist in bulls with chronic trypanosomiasis which are later subjected to chemotherapy.     

Salmon in New Zealand with special reference to the quinnat salmon

Of the 3 species of salmon successfully acclimatised in New Zealand, the quinnat, Oncorhynchus tshawytscha (Walbaum) is the most widespread. It is found mainly in the east coast rivers of the South Island. Although adults live in the sea and return to freshwater to breed, lake populations have developed either voluntarily or because egress to the sea is blocked by dams. Sea-living adult quinnat salmon return to rivers in summer to spawn in their natal streams and once in freshwater, cease feeding and the gut degenerates. Eggs laid by the females in redds are fertilised by the male, after which both parents die. Most young salmon emerging from the redds migrate downstream but their fate is uncertain. The few remaining feed and grow and migrate to sea in early summer. Examination of the ridges on fish scales reveals information about migration patterns which assists in studies conducted by the Ministry of Agriculture and Fisheries in the Glenariffe Stream. Marking and tagging of smelts is expected to provide information on survival to adult return and on movements of salmon at sea. The quinnat is the salmon species most favoured by anglers and it is also considered to have a commercial future in New Zealand, using the method of ocean ranching.