Genetic control of immunity to Eimeria tenella. Interaction of MHC genes and non-MHC linked genes influences levels of disease susceptibility in chickens.

The relative importance of MHC genes and background genes in the genetic control of disease susceptibility and the development of protective immunity to E. tenella infection was investigated in eight different strains of 15I5-B congenic and four inbred chicken strains. RPRL 15I5-B congenic chickens that share a common genetic background but express different B haplotypes demonstrated wide variations in disease susceptibility and the development of acquired resistance to E. tenella infection. Infection of chickens sharing a common B haplotype but expressing different genetic backgrounds showed quite contrasting levels of susceptibility to secondary E. tenella infection. In all chicken strains examined, infected chickens developed high levels of serum and biliary anti-coccidial antibodies regardless of their B haplotypes. Furthermore, no correlation between antibody levels and the phenotypically expressed levels of disease resistance was demonstrated. These findings lend support to the view that interaction of MHC genes and non-MHC genes influences the outcome of host response to E. tenella infection.

Experimental toxoplasmosis in Japanese quail.

Twenty-four 5-month-old battery-hatched Japanese quail were inoculated orally with 10(5) (ME 49 strain, group A, 6 birds), 10(3) (ME 49 strain, group B, 6 birds), 10(5) (GT-1 strain, group C, 6 birds), and 10(3) (GT-1 strain, group D, 6 birds) Toxoplasma gondii oocysts. All birds in group C died or were euthanized within 8 days after inoculation (DAI). Five of the 6 birds in group D died or were euthanized 8, 9, 15, 19, and 23 DAI. One of the 6 quail in group A died 9 DAI, and 1 of the 6 birds in group D died 16 DAI. The 11 quail (1 from group D and 10 from groups A and B) were euthanized 63 DAI; T. gondii was isolated by bioassays in mice from the brains of 10, hearts of 10, and skeletal muscles of all 11 quail. Quail that survived marked small intestinal and splenic toxoplasmosis lived long enough to develop severe protozoal pneumonia, myocarditis, or meningoencephalitis. The quail that survived only to be examined at 63 DAI had moderate multifocal nonpurulent encephalitis and myositis and had a hypertrophic spleen that contained hemosiderin-laden macrophages. Toxoplasma gondii antibodies were found in the sera of all quail examined 63 DAI. Antibody titers to T. gondii in the modified agglutination test were higher than in the indirect hemagglutination and latex agglutination tests. Antibodies were not detected in quail sera examined by the Sabin-Feldman dye test.

Important parasites in poultry production systems.

Poultry now accounts for 30% of all meat consumed. Parasites are a problem where ever poultry are raised, whether in large commercial operations or in small back-yard flocks, and economic losses can be significant. This paper will briefly review the major protozoan, helminth, and arthropod species in poultry including pathogenesis. Other topics will include the importance of the interaction of other diseases and parasites, and control of the infection by chemotherapy, management, and immunity.

Changes in liver glycogen of broilers during coccidiosis.

Liver glycogen levels of broilers with Eimeria acervulina, E. Brunetti, or E. tenella fell during the acute phase of the infection with the maximum effect at 5-6 days post-inoculation (DPI). During the early recovery phase (6-8 DPI), liver glycogen levels in the E. acervulina-infected birds increased to levels up to 3 times greater than those found in uninoculated control birds. A lesser increase was occasionally seen in E. tenella-infected birds. Pair feeding studies showed that the decrease in liver glycogen was not related to the amount of feed consumed. The magnitude of the glycogen overshoot at 7 DPI was not related to the depression of weight gain at 5 and 6 DPI. When feed was withheld from birds, liver glycogen levels of uninoculated control birds fell rapidly within 1 h after feed withdrawal. In birds infected with E. acervulina, liver glycogen levels remained high even after 3 h starvation. Injection of glucagon indicated that glycogen could be mobilized in both infected and uninfected birds.

Influence of dietary aflatoxin on the severity of Eimeria acervulina infection in broiler chickens.

Broiler chicks (Hubbard x Hubbard) receiving 2.5 microgram of aflatoxin/g of diet and inoculated with sporulated oocysts of Eimeria acervulina gained significantly less weight than chicks receiving either aflatoxin or coccidia alone. Aflatoxin alone affected body weight more in females than males. Blood parameters, however, showed no sex-related differences to E. acervulina or aflatoxin. E. acervulina had no effect on packed cell volume, red cell number, or hemoglobin levels. Gross lesions in the intestine caused by the coccidia appeared the same with or without dietary aflatoxin. Either aflatoxin or E. acervulina alone reduced the plasma pigment. When both were present, depigmentation was greater with some strains of coccidia than with either alone. Aflatoxin alone reduced the plasma levels of cholesterol and protein. The effect of E. acervulina on cholesterol or protein, with or without aflatoxin, depended on the coccidial strain used.

Nutrient absorption and changes in blood plasma of stunted broilers.

Broilers were collected from three farms in which there was high mortality, stunting, and leg weakness characteristic of a condition referred to by various names, including infectious stunting, pale bird syndrome, malabsorption syndrome, and helicopter disease. Broilers were also collected from a fourth farm in which no birds showed the syndrome. Most but not all of the stunted broilers exhibited paleness, poor feather development, and broken feather shafts. Most lesions and abnormalities of the internal organs were of low frequency and not correlated with stunting. Bleaching of the pancreas, however, was found in 47% of the stunted broilers. Compared with normal-sized broilers from the same farms, the stunted broilers had increased plasma protein, decreased plasma pigment, and a sometimes increased liver glycogen level. The increase in protein was the result of increased levels of alpha, beta 1, gamma 1 and gamma 2 globulins. The levels of plasma glucose, body temperature, breast muscle moisture, packed cell volume, and intestinal pH were not affected in stunted broilers. Likewise, no difference could be demonstrated between stunted and normal broilers in the in vitro intestinal absorption of glucose or L-methionine.

Comparison of disease susceptibility and subclass-specific antibody response in SC and FP chickens experimentally inoculated with Eimeria tenella, E. acervulina, or E. maxima.

Susceptibility to disease and the subclass-specific antibody response to Eimeria tenella, E. acervulina, and E. maxima were compared in two inbred strains of chickens, FP (B15B21) and SC (B2B2). FP strain was more susceptible to coccidiosis than SC chickens based on oocyst production, lesion score, and clinical signs. FP chickens infected with E. tenella had more severe cecal lesions and a significantly lower hematocrit level than SC chickens. FP chickens infected with E. acervulina excreted five times as many oocysts at 6 days postinfection as SC and showed a 71% reduction in plasma carotenoid level compared with controls (56% reduction in SC chickens). Body-weight change did not correlate with other signs of disease. Both SC and FP chickens produced high levels of serum IgM and IgG and biliary IgA. Although SC chickens had a slightly higher antibody response than FP chickens at 7 days postinoculation, both strains maintained high levels of IgM, IgG, and IgA for a prolonged period post primary inoculation. Although SC and FP chickens show different disease susceptibility to coccidiosis, they demonstrate similar antibody response.

Interaction of low-pathogenicity reoviruses and low levels of infection with several coccidial species.

Various combinations of reoviruses and coccidia were studied to see if interactions would occur. Two reoviruses were used: virus 2035, a moderate to low pathogen, and virus 2177, a nonpathogen. Coccidia used were Eimeria acervulina, E. mitis, and E. maxima at dosages of 10(3) or 10(4) sporulated oocysts/chick and E. brunetti at 10(4) sporulated oocysts/chick. In Hubbard-Hubbard cockerels, a combination of virus 2035 and E. acervulina (10(4) oocysts/chick) or E. maxima (10(3) oocysts/chick) significantly (P less than or equal to 0.05) increased the frequency of stunting (% of chicks with body weight less than 80% of controls) and further depressed weight gain over that seen with either virus or coccidia alone. Conversely, virus 2177 ameliorated the same effects in Shaver-Arbor Acre cockerels given 10(4) oocysts/chick of E. mitis or E. maxima. The interaction could not be attributed to changes in the degree of coccidial infection based on oocyst production. Reovirus did not generally change the effect of coccidia on levels of plasma pigment and plasma protein. In Hubbard-Hubbard cockerels, coccidia-induced effects were not ameliorated by virus 2177, suggesting that breed difference in interaction can be expected.

Concurrent infections with reoviruses and coccidia in broilers.

These experiments investigated the interaction among two species of coccidia (Eimeria acervulina and E. mitis) and three strains of reovirus (virus 2035, a weak to moderate pathogen; and viruses 2408 and 1733, severe pathogens). When reoviruses were not present, high inoculation dosages (10(6) sporulated oocysts/bird) of both E. acervulina and E. mitis depressed weight gain, plasma pigment, and plasma protein. Low doses of coccidia (10(4) oocysts) in the absence of virus had no such effect on weight gain. When high doses of coccidia were present at the same time as virus 2035 or 2408, they resulted in a significantly greater depression of weight gain than when either virus or coccidia were present alone. With virus 2035, this greater depression was seen even when low doses of coccidia were used. Lesion scores due to coccidiosis and the number of oocysts produced were not affected by previous exposure to reovirus. Both coccidiosis and reovirus infections increased the frequency of some leg problems and other abnormal conditions. The most obvious interaction between coccidia and reovirus was the marked increase in swollen hocks seen when coccidia and virus 2035 were present together (20-27%) compared with either the virus or coccidia alone (0-10%). Virus 2408 interfered slightly with the development of immunity to coccidia. There was some indication that early coccidiosis could increase the ability of some virus isolates to infect various tissues of the host.

Coccidiosis and intestinal pH in chickens.

The intestinal contents of white Leghorn cockerels were significantly lower in pH in birds infected with Eimeria mivati, E. maxima, or E. necatrix than in uninoculated control birds. The particular Eimeria species used affected the region of the intestine involved, the days (5-9 postinoculation) on which pH decreased, and the magnitude of the decrease. The effects on the magnitude and frequency of pH decrease were as follows: E. mivati, marked in the duodenum and jejunum, variable in the ileum; E. maxima, slight in the duodenum, variable in the jejunum and ileum; E. necatrix, no change in the duodenum, variable in the jejunum and ileum. Infection with E. tenella did not change the intestinal pH. The pH of the gizzard was occasionally higher in birds infected with E. mivati or E. necatrix than in uninoculated control birds. With all four species, on some days the pH in the ceca was higher than in the ceca of controls. These results and previous reports indicate that infection with one of the above four species or with E. acervulina or E. brunetti produces the greatest and most consistent decrease in pH in the region of the intestine where the particular species characteristically produces the severest infection.

Changes in carotenoid and vitamin A levels in young turkeys infected with Eimeria meleagrimitis or E. adenoeides.

Changes in levels of plasma xanthophyll, plasma retinol, liver retinol, and liver retinylpalmitate in poults infected with Eimeria meleagrimitis or E. adenoeides were measured by high-performance liquid chromatography. Infection with either species significantly reduced total plasma carotenoids; the reduction was due largely to a decrease in xanthophyll to approximately 50% of control levels on the day of maximum effect. In addition, E. meleagrimitis infection decreased plasma retinol levels from 1.84 microgram/ml plasma (controls) to 1.00 microgram/ml plasma on day 6 postinoculation. Concomitantly, liver retinol levels fell from 0.23 microgram/mg protein (controls) to 0.15 microgram/mg protein, and liver retinylpalmitate levels fell from 0.74 microgram/mg protein (controls) to 0.44 microgram/mg protein. In contrast, Eimeria adenoeides infection caused little change in either plasma or liver retinol levels.

In vivo role of tumor necrosis-like factor in Eimeria tenella infection.

The effect of tumor necrosis-like factor (TNLF) on the pathogenesis of coccidiosis was investigated. Injection of crude chicken TNLF enhanced the weight loss caused by Eimeria tenella infection. Rabbit polyclonal antibody against recombinant human tumor necrosis factor-alpha (rhTNF) partially restored E. tenella-induced weight loss in SC chickens, but not in TK chickens. However, injection of chickens with chicken TNLF, rhTNF, and rabbit serum against rhTNF had no significant effect on cecal lesions. Both SC and TK chickens produced circulating TNLF following primary, but not secondary infection, and SC chickens showed higher level of TNLF production than TK chickens. Peripheral blood leukocyte-derived macrophages from SC and TK chickens produced a significant amount of TNLF compared to the preinfection condition when cocultured with sporozoites. In general, macrophages from SC chickens produced higher levels of TNLF than those from TK chickens. No significant difference was observed between primary and secondary infection. These results suggest that the excessive TNF production may be involved in weight loss caused by E. tenella infection in SC chickens.

In vitro and in vivo characterization of avian reoviruses. II. Clinical evaluation of chickens infected with two avian reovirus pathotypes.

The effect of two avian reovirus isolates (2408 and 1733) on digestion and nutrient metabolism in infected chickens was assessed by an in vitro absorption assay and clinical blood chemistry analysis. Birds of various ages were inoculated orally and intratracheally with reovirus and sampled periodically for the respective assays. Transitory malabsorption was observed in the duodenum of birds infected with reovirus 2408. Conversely, increased absorption was detected in the ileum of these same birds. Clinical blood chemistry analyses of birds infected with both isolates revealed that severely affected birds had abnormally elevated plasma total protein, plasma albumin, and calcium levels. Decreases were found in percent bone ash and, due to abnormally high globulin levels, in albumin:globulin (A:G) ratios. A significant (P less than 0.05) correlation between body weights and total protein, albumin, A:G ratio, and bone ash was found in infected birds. The most pronounced metabolic and physiologic changes occurred in the severely affected birds, and, in general, pathogenicity of the isolates was reflected by the degree of metabolic change.

Characterization of the toxicity of the mycotoxins aflatoxin, ochratoxin, and T-2 toxin in game birds. I. Chukar partridge.

Chukar partridges were fed diets containing 1.25, 2.5, or 5 ppm aflatoxin; 1, 2, or 4 ppm ochratoxin A (OA); or 4, 8, or 16 ppm T-2 toxin. Toxin-induced mortality was seen during the third week with 4 ppm OA (12.5%) and 16 ppm T-2 toxin (15%), compared with the mortality in control chukars fed no toxin (2.5%). Body weights were significantly decreased by the highest level of aflatoxin at 3 weeks of age, by the highest level of OA by 2 weeks of age, and by 8 and 16 ppm T-2 toxin by 1 week of age. Aflatoxin did not affect liver weight and OA did not increase kidney weight in 3-week-old chukars. There was a slight decrease in kidney weight in chukars fed 4 ppm OA; however, the decrease was related to the decrease in body weight produced by the toxin. Mouth lesions were seen at all levels of T-2 toxin fed.

Characterization of the toxicity of the mycotoxins aflatoxin, ochratoxin, and T-2 toxin in game birds. III. Bobwhite and Japanese quail.

Bobwhite and Japanese quail were fed diets containing 1.25, 2.50, or 5.00 ppm aflatoxin; 1, 2, or 4 ppm ochratoxin A (OA); or 4, 8, or 16 ppm T-2 toxin. Aflatoxin induced mortality in bobwhites during the second and third week with 1.25 ppm (10%), 2.50 ppm (30%), and 5.00 ppm (40%), and during the same period with T-2 toxin at 8 ppm (20%) and 16 ppm (22.5%). Body weights of bobwhite quail were significantly decreased by the two higher levels of aflatoxin by 2 weeks of age, and by the two higher levels of T-2 toxin by 1 week of age. In Japanese quail, only the highest level of aflatoxin and T-2 toxin reduced body weight (by 3 weeks and by 1 week of age, respectively), and even then to a much lesser extent than in bobwhites (less than 10%). Aflatoxin did not affect feed-conversion ratio (FCR) in bobwhite quail, but the two higher levels of T-2 toxin increased FCR. None of the toxins induced mortality or increased the FCR in Japanese quail. Aflatoxin increased liver weight in both bobwhite and Japanese quail. OA increased kidney weight in 3-week-old Japanese quail but had no effect on the kidney weight of bobwhite quail. Mouth lesions were progressively more severe in bobwhite quail fed increasing levels of T-2 toxin, but lesions were far less severe in Japanese quail.

Characterization of the toxicity of the mycotoxins aflatoxin, ochratoxin, and T-2 toxin in game birds. II. Ringneck pheasant.

Ringneck pheasants were fed diets containing 1.25, 2.5, or 5 ppm aflatoxin; 1, 2, or 4 ppm ochratoxin A (OA); or 4, 8, or 16 ppm T-2 toxin. Severe toxin-induced mortality was seen during the first to third weeks with 2.50 and 5.00 ppm aflatoxin (92.5% and 97.5%, respectively), compared with the mortality in control pheasants fed no toxin (0%). Slight mortality (less than or equal to 5%) was seen with OA and T-2 toxin. Body weights were significantly decreased by the lowest level (1.25 ppm) of aflatoxin by 2 weeks of age, by the two highest levels of aflatoxin by 1 week of age, and by 16 ppm T-2 toxin by 1 week of age. The feed-conversion ratio was increased by 2.50 and 5.00 ppm aflatoxin compared with the feed-conversion ratio in controls, although high mortality may have influenced the results. Aflatoxin had no effect on liver weight, but OA increased kidney weight in 3-week-old pheasants. Mouth lesions were seen in some of the pheasants fed T-2 toxin.

Effect of amprolium on production, sporulation, and infectivity of Eimeria oocysts.

Amprolium reduced the number of oocysts shed by Eimeria acervulina, E. maxima, E. necatrix, and a mixture of susceptible strains of E. tenella. Sporulation of oocysts from mediated chickens was reduced compared with that of oocysts from unmedicated chickens. Sporulation was reduced by levels of 0.0250% amprolium for E. acervulina and by levels of 0.0060% for E. maxima and the susceptible E. tenella. Not enough oocysts were recovered to measure sporulation of E. necatrix. Sporulation reduction was not affected by the method of administration of amprolium (feed or water), except with E. acervulina, for which fewer oocysts sporulated when 0.0120% amprolium was added in the drinking water than when 0.0125% amprolium was added to the feed. Conversely, amprolium medication had no effect on the sporulation of an amprolium-resistant E. tenella. When fed to unmedicated chickens, those oocysts from amprolium-medicated chickens that did sporulate were as infective as oocysts recovered from unmedicated chickens.

Effect of aging on survival and pathogenicity of Eimeria acervulina and Eimeria acervulina and Eimeria tenella.

After 6 to 8 months of storage, cultures of sporulated Eimeria acervulina and E. tenella oocysts ahd a marked drop in the number of sporocysts that survived grinding, sporozoites that survived after excystation, and sporozoites that penetrated chick kidney cells in vitro. The rate of excystation was unaffected by storage of up to one year. In vivo pathogenicity, based on weight gain, lesion score, and plasma pigment, declined after 5 months of oocyst storage. The reduction in pathogenicity in vivo could be compensated for by adjusting the inoculation dosage to reflect the loss of infectivity seen in the in vitro test.

Cyclocoelum mutabile infection and aortic rupture in an American coot (Fulica americana).

An American coot (Fulica americana) was found dead within the enclosed research compound of the South Central Poultry Research Laboratory at Mississippi State, Mississippi. Gross and microscopic examinations revealed the bird to be in good body condition; however, blood from the beak cavity and external nares was present. Biliary congestion, hemopericardium, blood-filled air sacs, and a ruptured, ascending aorta were also noted. Nineteen trematodes (Cyclocoelum mutabile) were found within the body cavity at necropsy. Bacteriological examination revealed the presence of Escherichia coli in both the heart and liver and Pseudomonas putida in the liver only. No virus was isolated.

Interaction of aflatoxin with Eimeria tenella infection and monensin in young broiler chickens.

Young broiler chicks inoculated with Eimeria tenella and given a diet containing 2.5 mug aflatoxin/g had significantly higher mortality than birds with aflatoxicosis or coccidiosis alone or uninoculated controls. This effect was seen even when a light coccidial infection alone did not increase mortality or cause weight depression. In addition this higher mortality with the combination began earleir and occurred at a higher rate than did mortality from aflatoxin or cecal coccidiosis alone. Dietary monensin sodium (99 umg/g) did not completely prevent mortality and weight depression when aflatoxin and E. tenella were in combination. Aflatoxin and E. tenella singly significantly depressed three-week body weights; however, the depression was most severe when the two were in combination. Both dietary aflatoxin and E. tenella significantly reduced hemoglobin, packed cell volume, and plasma pigmentation, and in combination resulted in more severely reduced hemoglobin, packed cell volume, and plasma pigmentation. Coccidial lesion scores were significantly less for the combination of E. tenella and aflatoxicosis than for coccidiosis alone. This atypical response of the ceca to E. tenella in the presence of dietary aflatoxin was characterized by less distended ceca, very little coagulated blood in the ceca, and apparently more profuse cecal hemorrhage.