The influence of dietary protein on live bodyweight, degree of anaemia and erythropoietic responses of Scottish Blackface sheep infected experimentally with Trypanosoma congolense

The present study investigated the influence of dietary protein on the intensity of parasitaentia, degree of anaemia and erythropoietic responses, in sheep experimentally infected with Trypanosoma congolense and given either a high protein diet (116 g digestible crude protein [dcp] per day) or a low protein diet (51·5 g dcp per day). It was observed that infected and control animals on the high protein diet grew at similar rates while infected animals on the low protein diet experienced marked retardation of growth compared with their uninfected controls. Dietary protein had no influence on the degree of anaemia that followed infection. Measurement of blood volumes revealed that low protein infected group had significantly lower mean circulating red cell volume than their controls. Ferrokinetic measurements indicated that plasma iron turnover rates (pitr) and ⁵⁹Fe incorporation rates were higher in the high protein infected group than in the low protein infected group, although these differences were not significant. These observations indicate that infected animals on a high protein tended to show greater enhancement of erythropoietic activity that infected animals on low protein diet.     

Pathophysiological studies on Dicrocoelium dendriticum infection in sheep

Red cell kinetics and plasma protein metabolism were investigated in two experiments using 20 adult sheep naturally infected with Dicrocoelium dendriticum, but free of other liver and gastrointestinal helminths. In the first experiment, where groups of animals with low to high Dicrocoelium burdens were injected with 51Cr-labelled red cells and 125I-labelled albumin, the results indicated that there were no significant differences in the turnover rate of labelled red cells or albumin between any of the groups. In the second experiment, two groups of sheep with low and high worm burdens were studied using the same radioisotope tracers; in addition, 59Fe-citrate was used to assess red cell iron incorporation rates in the two groups. Although the red cell half-lives of the infected sheep were just significantly longer, both were within normal limits and the difference was attributed to random variation within the two small groups of sheep. No significant differences were found in the other parameters. It was concluded that burdens of up to 4000 D. dendriticum do not cause significant blood or plasma protein loss in sheep.     

The effect of dietary protein on the pathophysiology of acute ovine haemonchosis

An experiment was conducted to examine the effect of dietary protein on the pathophysiology iof acute haemonchosis in Finn Dorset/Dorset horn lambs.

Erythrokinetic and metabolic studies using ⁵¹Cr-red cells, ⁵⁹Fe-trasferrin and ¹²⁵I-albumine and digestive efficiency and nitrogen balance measurements wer conducted between 19 and 39 days after infection. Identical radioisotopic and nutritional studies were conducted later on pair-fed control lambs.

The results demonstrated that lambs on a law protein diet (88 g crude protein (CP) kg⁻¹ dry matter (DM)) were less able to withstand the pathyphysiological consequences of infection with 350 Haemonchus contortus larvae kg⁻¹ body weight than lambs given a high protein (170 g CP kg⁻¹ DM) diet, despite similar worm budens.

Erythrokinetic studies indicated that abomasal blood loss was similar in both groups of infected lambs, and circulating red cell volumes were reduced and plasma volumes were expanded to a similar degree in both groups. The majority of infected lambs in both dietary groups responded equally well to the gastric haemorrhage by increasing the rate of red cell production and their absorption of dietary iron was greater than in the control lambs. Albumin catabolism was increased in both groups of infected lambs, particularly in those given the low protein diet.

Within each dietary group there were no differences in the digestibilities of the various proximate fractions of the experimental diets and no differences in the urinary of faecal nitrogen losses between infected lambs and their pair-fed control. However, loss of appetive was a major feature of the disease, particularly in the lambs given the low protein diet and this feature appeared to be crucial in determining the ability of the infected sheep to withstand the pathophysiological effects of the parasite.     

Blood parameters and turnover data in calves infested with lice.

Erythrokinetic and plasma protein turnover studies using 51Cr-red cells, 59Fe-transferrin and 125I-albumin, were carried out on young Ayrshire calves naturally infested with the long-nosed sucking louse Linognathus vituli. Throughout the trial none of the animals lost their appetite. Liveweight gain was greater in the uninfested animals but not significantly so. The infestation did not cause the animals to become anaemic, but plasma iron turnover rates were decreased and there was a significant increase in the red cell survival time. The circulating volumes of red cells and plasma were not significantly affected and the fractional catabolic rate of albumin was not markedly altered. At the end of the trial the mean red blood cell and mean total blood content of one louse was evaluated at 0.157 microliters and 0.443 microliters respectively, using 51Cr, and 0.120 microliters and 0.350 microliters respectively, using 59Fe. Using 125I the mean albumin content of one louse was 98.4 micrograms.     

Influence of dietary protein on the pathophysiology of ovine haemonchosis in Finn Dorset and Scottish Blackface lambs given a single moderate infection

Two experiments were conducted to examine the influence of dietary protein on the pathophysiology of Haemonchus contortus in lambs of two breeds, namely Finn Dorset and Scottish Blackface. Erythrokinetic and metabolic studies using 51Cr-red cells, 59Fe-transferrin and 125I-albumin, and digestive efficiency and nitrogen balance measurements were conducted between four and six weeks after infection. Identical radioisotopic and nutritional studies were also conducted on pair-fed control lambs of both breeds. The results demonstrated that in normal control animals, there were no significant effects of diet or breed on any of the erythrokinetic, metabolic or nutritional parameters, with the possible exception of red cell survival which was considerably longer in the Finn Dorset lambs. However, in the infected animals diet and breed did influence those parameters. The severest effects were seen in the infected Finn Dorset lambs given the low protein diet. These animals had the highest level of abomasal blood loss and this was associated with low red cell volumes and high levels of both albumin catabolism and plasma iron turnover. These animals were also in negative nitrogen balance which was partly accounted for by a significantly greater urinary nitrogen loss compared with their pair-fed controls and partly due to the poorer digestibility of the crude protein fraction of the diet. In contrast, although the infected Scottish Blackface lambs had high levels of blood loss and associated pathophysiological changes, these did not differ between dietary treatments and were similar to the changes in the infected Finn Dorset lambs given the high protein diet.     

Listeriosis in Sheep: Eperythrozoon Ovis Infection Used as a Model to Study Predisposing Factors

Three groups of 9 months old lambs, each group consisting of 5 animals, were infected experimentally with Eperythrozoon ovis (Eo), Listeria monocytogenes (Lm) and Eo/Lm, respectively. The animals infected with Eo developed haemolytic anaemia, but otherwise no clinical symptoms were seen. The animals infected with Lm had a period with fever and reduced appetite after infection. These symptoms lasted longer and were more pronounced in the group with the dual infection (Eo/Lm). None of the lambs developed clinical meningo-encephalitis during the experiment.Group Lm developed the highest reciprocal geometrical mean titres against Lm. No titer rise was found in group Eo, while group Eo/Lm had a slight rise towards the end of the experiment. Group Eo/Lm also had the strongest delayed hypersensitivity reaction against Lm.After Eo infection, a fall in packed cell volume, haemoglobin, number of red cells, and plasma glucose and an increase in serum iron were recorded. Serum iron dropped and serum copper increased after infection with Lm.In this experiment the blood changes induced by Eo, i.e. haemolytic anaemia and acidosis, led to a prolonged state of illness in animals infected with Lm, in addition to inhibited development of antibody titres, but not to clinical meningoencephalitis.     

Demonstration of erythrophagocytosis in Trypanosoma congolense-infected goats

Anaemia is the most prominent clinical sign of trypanosomosis in domestic animals but little is known about its pathogenesis. This work investigated erythrophagocytosis as the possible cause of anaemia. Pathogenic Trypanosoma congolense (IL3000) was intravenously inoculated into six goats at 3x10(6) trypanosomes per goat. Six other goats were maintained as controls. The infection was studied for 10 weeks and parasitaemia, packed cell volume (PCV) and serum protein levels were determined. The amount of erythrophagocytosis was determined from the amount of 51Cr-labelled red blood cells (RBCs) phagocytosed by self mononuclear cells (MNCs) in vitro and by microscopically counting phagocytosed RBCs on Giemsa stained smears of incubated mixtures of RBCs and self MNCs. The infection resulted in trypanosomosis with rapid progressive anaemia and mean peaks of parasitaemia of about 3x10(3)ml(-1). In infected goats, a significant (P<0.05) mean reduction in PCV (of 37-22%) was observed starting from about 20 days up to 56 days post-infection. Within this same phase, significant (P<0.05) differences in mean radioactivity counts of (51)Cr incorporated into MNCs were observed with infected goats' samples having counts 50% higher than the control goats' samples. Microscopically, the mean number of phagocytosed RBCs in infected goats' MNCs was noted to be 80% higher (P<0.05) than that of control goats. Appreciable increases (P<0.05) in mean serum globulin levels, from 3.5 to 4.7g/dl, were observed within 3 weeks of infection. The study showed that erythrophagocytosis is an important mechanism leading to anaemia in the pathophysiology of T. congolense infection in Zambian goats.     

Intestinal plasma and blood loss in piglets infected with Strongyloides ransomi

Five piglets were infected subcutaneously with 10 000 third-stage larvae of Strongyloides ransomi per kg body weight; another five animals served as controls.Simultaneous measurement of plasma and red cell loss into the intestinal tract in infected and control animals have been carried out using porcine albumin labelled with ⁹⁵Nb and red cells labelled with ⁵¹Cr. Between the 10th and 20th days the daily average “clearance” of plasma was significantly greater in the infected animals (111.9 ml) than in the controls (18.8 ml). Daily average “clearance” of red cells was 4.1 ml in the infected group and 0.83 ml in the control group. By comparing the faecal “clearance” of plasma and red cells between the infected and control animals, it would appear that there is a leakage of plasma into the gut which is greater than can be accounted for in terms of whole blood loss.     

A study on the treatment of theileriosis in sheep using “Miejiaoming”

We once tried to treat sheep and goats suffering from theileriosis caused byTheileria hirci using Berenil, Primaquine phosphate, etc. but the cure rate never exceeded 88%. Afterwards we used ‘Miejiaoming’ produced by ourselves and the curative effect was improved significantly. Altogether 33 diseased sheep with ages ranging from 1·5–4 months and with infected red blood corpuscle rates of over 5% were treated in 2 groups. The first group, of 18 sheep, was treated with a dosage of 0·1 millilitre per kilogram body weight and the second group, of 15 sheep, with a dosage of 0·15 millilitre per kilogram body weight. Every diseased sheep was given a daily injection of “Miejiaoming” for 2–4 days. One sheep in the first group was treated four times. Its temperature was reduced from 41·1°C to 40·0°C and its infected red blood corpuscle rate from 36·7% to 2·1%, but it suffered from severe anaemia and heart failure and died on the sixth day. All other sheep in the two groups were cured: the cure rate for the first group was 94·4% and for the second group 100%. In addition, the medicine has been used in regions such as Shanxi Province for treatingTheileria annulata, T. sergenti andBabesia bovis of cattle with satisfactory results.

     

Immunosuppression in deer mice with experimentally induced trypanosomiasis.

Light and electron microscopic examinations of deer mice (Peromyscus maniculatus) chronically infected with Trypanosoma equiperdum revealed hyperplasia of germinal center lymphocytes (germanocytes) in the lymph follicles of spleen and lymph nodes and infiltration of the splenic red pulp cords and nodal medullary cords with plasma cells. Proliferation and infiltration of plasma cells caused disruption of the B- and T-lymphocyte areas in these organs. Stimulation of splenic lymphocytes in vitro by phytohemagglutinin and concanavalin A revealed marked depression in T-lymphocyte response; stimulation with lipopolysaccharide and pokeweed mitogens showed depression of B-cell response. Deer mice infected with virulent trypanosomes had decreased immunologic response to injection of sheep red blood cells, whereas deer mice given radioattenuated trypanosomes had normal to enhanced immunologic response to injection of sheep red blood cells.     

Pathophysiology of ovine fascioliasis: The influence of dietary protein and iron on the erythrokinetics of sheep experimentally infected with Fasciola hepatica

Worm-free sheep were fed diets with a high or low protein and iron content and infected with 1,000 F. hepatica metacercariae. The adult fluke burdens of the sheep on each diet were similar, but animals on the poorer plane of nutrition developed an earlier and ultimately more severe anaemia and as a result had to be necropsied earlier. By measuring the attendant changes in blood volume and erythrokinetics, it was found that the underlying cause of the anaemia in all animals was a combination of haemodilution, intra-hepatic and biliary haemorrhage, and its earlier appearance and faster development in the poorer-fed group was a refelection of the earlier onset of these changes in association with a faster rate of fluke migration. The ultimate degree of anaemia was not related to the severity of biliary haemorrhage, but rather to the animals' erythropoietic capacity. This was substantially lower in the sheep maintained on the poorer diet, which unlike their better-fed counterparts, became iron deficient by virtue of their inability to replace from the diet iron lost in the faeces as a result of haemorrhage. It was concluded that this difference was primarily a reflection of the better appetite and hence iron intake of the supplemented sheep, but differences in the efficiency of dietary iron utilization, possibly related to protein intake, may also have been involved.In a further experiment involving sheep infected with 600 metacercariae, there was no evidence of haemodilution. When provided with a diet of high protein and iron content, these animals were able to maintain constant, albeit reduced PCV values in the face of substantial biliary haemorrhage. However, when switched to an inferior diet, the same degree of haemorrhage produced a sharp fall in PCV, suggesting that erythropoiesis was adversely affected by reduced protein and iron intake.     

Clinical pathology of experimental Schistosoma curassoni infections in sheep and goats

The clinical pathology of Schistosoma curassoni infection in sheep and goats was studied for 22 weeks following experimental infection with 7000 and 4000 cercariae, respectively. Excretion of eggs began at week 7 after infection: in goats the numbers increased to 30 to 50 eggs per gram faeces (epg) at weeks 8 to 18, followed by a reduction. In a pregnant goat, epg values increased markedly before and after parturition. The mean faecal egg counts in sheep were lower than in goats, increasing to a maximum level of 30 epg at weeks 16 and 17 after infection. Infected sheep maintained growth rates roughly comparable with controls, whereas infected goats failed to gain as much weight as the controls. Infected goats and sheep produced eosinophil counts of about 3 x 10(3) mm-3, five and eight weeks after infection, respectively. Sheep developed a progressive anaemia from week 11 after infection, in goats blood values remained within normal limits. Differences in serum protein concentration were observed between infected and uninfected goats about nine weeks after infection, but not in sheep. Increased total protein values, hyperglobulinaemia and lowered albumin to globulin ratios were features of infected goats. Serum glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, gamma-glutamyl transferase, total lactate dehydrogenase and bilirubin were not significantly changed. The mean recovery in sheep was 608 worms, in goats 428 worms, but the total tissue egg counts were higher in the latter. Of the total eggs deposited in the goats 92 per cent were found in the liver with 51.5 per cent in the ovine liver. The histopathological changes were studied.     

Pathophysiology of Haemonchus placei infection in calves.

This study was conducted to investigate the pathophysiology of Haemonchus placei infection in Friesian calves. Seven calves were divided into two groups, three uninfected calves (control group) and four infected animals. The latter group were infected orally with 500 H. placei larvae kg-1 body weight. Five weeks after infection they were all housed in metabolic crates and injected with 125I-bovine albumin. 51Cr-red cells and 59Fe-transferrin, to study albumin metabolism, erythrokinetics and ferrokinetics. The results showed that there was a significant reduction in the mean haematocrit values and reduced weight gains in the infected calves compared with the controls. There was also a change in the distribution of albumin from the extravascular to the intravascular pool and a significant increase in the plasma and blood volumes of infected calves although the blood and albumin loss via the gastrointestinal tract recorded in this study was similar in both groups.     

The pathophysiology of ovine trypanosomosis: haematological and blood biochemical changes.

The course of Trypanosoma congolense infection in sheep was followed for 96 days. Infected animals developed fluctuating parasitaemia, macrocytic normochromic anaemia and leucocytosis which was principally a lymphocytosis. Following treatment with the trypanocidal drug, diminazene aceturate at 84 days after infection, the haematological values returned to normal within 12 days. Infected sheep developed hypocholesterolaemia and hypophospholipidaemia leading to a reduction in total serum lipids. This study has shown that sheep infected with T. congolense develop anaemia, the onset of which follows the first wave of parasitaemia. The changes in blood lipids observed in infected sheep appeared to be related to the intensity and duration of parasitaemia.     

Effect of Eperythrozoon ovis infection on the reductive potential of sheep erythrocytes

Reduced glutathione (GSH) and methaemoglobin were measured in sheep blood during an infection cycle of Eperythrozoon ovis and in uninfected control blood. The GSH levels in infected erythrocytes were significantly lower in the latter half of the infection cycle. Incubation with acetylphenylhydrazine (APH) resulted in negligible leves in infected cells whereas control cells were approximately 45% normal. Infection with E. ovis had little effect on methaemoglobin levels. However, incubation with APH caused a marked increased of the methaemoglobin levels in both infected and control blood; the control methaemoglobin levels were significantly higher.It was concluded from these observations that E. ovis interfered with maintenance of GSH within erythrocytes to an extent that when challenged with an oxidizing chemical erythrocyte membrane integrity could be lost. In addition E. ovis may bave provided some protection against oxidative damage for the heme portion of the haemoglobin molecule or the amount of oxidative damage to haemoglobin was further advanced in the infected cells.     

In vitro erythrophagocytosis by cultured macrophages stimulated with extraneous substances and those isolated from the blood, spleen and bone marrow of Boran and N'Dama cattle infected with Trypanosoma congolense and Trypanosoma vivax

A standard radioactive chromium (51Cr) release assay was used to assess the in vitro phagocytosis and lysis of bovine erythrocytes by cultured splenic, bone marrow and peripheral blood monocyte-derived (PBM) macrophages isolated from healthy and Trypanosoma congolense and T. vivax-infected cattle of the Boran and N'Dama breeds. Recombinant cytokines (rHuTNF-alpha and rBolFN-gamma) and non-acid-dialysed peripheral blood mononuclear cell (PBMNC) culture supernatants stimulated these PBM for enhanced activities. The stimulants caused increases in the rate of erythrocyte phagocytosis and lysis by cultured PBM in a concentration-dependent manner. But very high stimulant concentrations caused deceased in vitro erythrophagocytosis. However, bacterial lipopolysaccharide (LPS) and acid-dialysed PBMNC culture supernatants did not cause any increase in cultured PBM erythrophagocytosis. In vitro erythrocyte phagocytosis and lysis by splenic, bone marrow and peripheral blood monocyte (PBM)-derived macrophages of Boran breed of cattle infected with Trypanosoma congolense increased from 14 days post-infection (DPI) onwards and thereafter maintained at various levels above pre-infection. Cultured splenic macrophages showed the greatest erythrocyte destruction capability while PBM-derived macrophages was the least. The rates of in vitro erythrocyte phagocytosis and lysis were higher with the cultured PBM of the Boran than those of the N'Dama cattle during T. congolense infection. The rate of in vitro erythrocyte destruction was however, similar in both groups of cattle during T. vivax infection. These results correlated positively with the dynamics and degree of anaemia developed by these groups of animals during both T. congolense and T. vivax infections. Cattle infected with T. congolense and T. vivax developed varying degrees of normocytic normochromic anaemia during infection. Boran cattle developed a more severe anaemia, and had to be treated with diminazine aceturate, than N'Dama cattle during T. congolense infection. Both breeds of cattle developed a milder but similar degree of anaemia during T. vivax infection. None of the animals were treated. The results of this study indicated a role of in vivo macrophage stimulatory factors, notably cytokines such as TNF-alpha and IFN-gamma in host's serum, as well as parasite antigens, which may act singly or in concert, in the process of enhanced erythrocyte destruction, hence anaemia by the mononuclear phagocytic system (MPS) during bovine trypanosomosis.     

Ferrokinetic studies in normal and iron deficiency anemic calves.

Ferrokinetic studies were performed on control calves and on calves with experimentally induced iron deficiency anemia, all 15 weeks old.The plasma iron clearance half time was about 4 times shorter in the experimental than in the control group. The low plasma iron concentration in the anemic calves was partially compensated by a more rapid plasma iron disappearance. Therefore the difference in the plasma iron turnover rate was reduced.The mean value of plasma iron daily renewal rate was about 3 times higher in the experimental than in the control group.The maximum uptake of injected ⁵⁹Fe into blood cells was reached 14 to 16 days after injection. The uptake of ⁵⁹Fe was about 10% higher in the control than in the experimental group.Using the values from the ferrokinetic study, the iron need for calves could be estimated. The requirement of iron to maintain a normal and constant Hb in a calf weighing 100 kg at a growth rate of 1 kg/daily was estimated as being 17.5 mg/day. Based on information in the literature and assuming a retention of dietary Fe of 25%, the total daily iron need for such a calf gaining 1 kg/day would be 160–180 mg.     

59FE UTILISATION AND EXCRETION IN ANAEMIA OF CATTLE CAUSED BY PIMELEA TRICHOSTACHYA INTOXICATION

Experimental chronic Pimelea poisoning, with severe anaemia, was produced in 4 calves by daily oral dose rates of Pimelea trichostachya of between 20 to 60 mg/kg body weight of whole plant. Bone marrow function was studied before and during intoxication using 59Fe to determine plasma iron clearance rates, intraerythrocytic iron incorporation rates and percentage iron uptake, and faecal blood loss was measured before and during intoxication. It was shown that bone marrow activity was neither significantly depressed nor enhanced during intoxication. There was however, evidence of a slight increase in erythrocyte maturation rate. Reticulocytosis was not observed during the development of anaemia, but did occur in 3 of the calves shortly before death.     

Hepatozoon spp. (Apicomplexa: Hepatozoidae) infection and selected hematological values of the neotropical rattlesnake, Crotalus durissus collilineatus (Linnaeus, 1758) (Serpentes: Viperidae), from Brazil

This study aims to establish the hematological values of Crotalus durissus collilineatus snakes captured in Brazil as well as to verify the effects of hematozoan infection on these snakes. Eighty-three blood samples were drawn from C. d. collilineatus specimens for analysis. The sample set was composed of 30 males and 30 females, recently caught from the wild, and 11 males and 12 females bred in captivity. Blood samples were used to determine red blood cell counts, white blood cell counts, thrombocyte counts, hematocrit values, hemoglobin concentration, and total plasma protein. Blood smears were used to diagnose Hepatozoon spp. infection and to calculate the parasitic load in the sample as well as the percentage of immature red cells. Results obtained for the wild-caught animals, with and without parasites, were compared among themselves and with the values obtained for the captive-bred animals. Hematological values for C. durissus were established. Wild-caught snakes had an infection rate of 38.3%, while no Hepatozoon sp. infection was detected in the captive-bred animals. The snakes which were not infected by the Hepatozoon sp. exhibited average weight, length, and weight-length ratios higher than those of the infected animals. An increase in immature red cells was noted in the Hepatozoon-infected snakes.     

Experimental production of congenital persistent swine fever infections: II. Effect on functions of the immune system

Twelve pregnant sows were infected at various stages of gestation with a low-virulent field strain of swine fever (SF) virus. The sows developed neutralizing antibody in serum, colostrum and milk.Only one pig had antibody to SF virus at birth. Twenty-three congenitally infected pigs developed a persistent viraemia. In the plasma samples of these pigs, neither antibodies nor virus-antibody complexes were detected after the disappearance of maternal antibodies.The persistently infected pigs showed a normal antibody response against sheep red blood cells, except in the terminal stage of disease. These observations indicate immunological tolerance to SF virus in these pigs. Immunological tolerance was also induced in pigs which had been infected in utero after the onset of immune competence.The lymphocyte response to phytohaemagglutinin seemed to be slightly depressed in the persistently infected pigs, whereas the response to pokeweed mitogen was comparable with that of control pigs.A clear, cell-mediated immune response to SF virus could not be demonstrated by the lymphocyte stimulation test.Three pigs that were born uninfected did not produce neutralizing antibody following natural exposure from in-contacts, whereas the littermates did. These pigs appeared to be sensitized when challenged with virulent SF virus.