Experimental infection of Newcastle disease virus in pigeons (Columba livia): Humoral antibody response, contact transmission and viral genome shedding

The aim of this study was to evaluate the humoral antibody response, the genome viral excretion and the contact transmission of pathogenic chicken origin Newcastle disease virus (NDV) from experimentally infected pigeons (Columba livia) to in-contact pigeon. The antibody response to infection was assessed by the hemagglutination inhibition (HI) test and the genome viral excretion was detected by RT-PCR. Viral strain induced high antibody levels, both in inoculated and in sentinel birds. The pathogenic viral strain for chickens was unable to produce clinical signs of the disease in experimentally infected pigeons, although it induced the Immoral antibody response and produced NDV genome shedding. NDV genome was detected intermittently throughout the experimental period, from 5 days post-infection (dpi) to 24 dpi. Therefore, viral genome shedding occurred for 20 days. The viral genome was detected in all birds, between I I and 13 dpi. Furthermore, the high infectivity of the virus was confirmed, as all non-inoculated sentinel pigeons showed antibody levels as high as those of inoculated birds. (C) 2007 Elsevier B.V. All rights reserved.

Experimental infection by Salmonella enterica subsp enterica serovar kottbus in day-old broiler chickens

The strain used in this work was a Salmonella enterica subsp enterica serovar Kottbus (6,8:e,h:1,5) isolated from imported day-old ducklings in Laboratório Nacional Agropecuário (LANAGRO/SP) of the Ministry of Agriculture of Brazil (MAPA). In view of the lack of information available about this Salmonella isolate and also because it was detected in day-old imported birds, this study was carried out to investigate the dissemination of S. Kottbus among newly hatched chicks. The birds were placed in three groups: one group of 20 birds received 0.1 mL of S. Kottbus culture containing 1.2 x 10(8) CFU/mL, the second group of 20 birds was inoculated with 1.2 x 10(5) CFU/mL and the third group of 10 birds was untreated (control group). Results were similar for both infected groups. The bacterium was recovered from cloacal swabs collected from the first day following the experimental infection until the end of the trial (42 days post-inoculation). At 15 and 42 days post-inoculation (dpi), half of the birds of each group were killed for bacteriological examination of cecal contents, liver and spleen. At 15 dpi, viable cell counts of S. Kottbus were obtained in all kinds of samples. At 42 dpi, Salmonella was present in the liver and spleen of few birds, but in large amounts in the cecal contents of almost all birds.

Experimental infection with Leishmania chagasi in immunosuppressed Balb/c mice: cytokines and parasite burdens

The immune response in leishmaniasis may result in a polarization of the T lymphocyte subpopulation, altering cell phenotype and resulting in immune protection or disease exacerbation. Leishmania may persist in the body either during asymptomatic infections or after treatment, which represents high risk under immunosuppression. The objective of this study was to evaluate the effect of infection with immunosuppression by dexamethasone associated with pentoxifylline on animal weight, spleen weight, spleen and hepatic parasitic load and immunopathology, as well as the IFN-gamma and IL-10 production in spleen cell culture of Balb/c mice infected with Leishmania chagasi. The infection did not cause body weight gain in animals, but both the weight and size of the spleen were increased. The immunosuppression using dexamethasone associated with pentoxifylline affected body weight gain and spleen weight and size in both infected and non-infected animals. The immunosuppression did not significantly alter the course of the splenic or hepatic parasite burden. Dexamethasone and pentoxifylline significantly affected cytokine production, but did not influence the Th1/Th2 ratio in infected animals.

Experimental infection of Leishmania chagasi in immunosuppressed balb/c mice: cellular immune response and parasite burden

The immune response to leishmaniasis can result in a polarization of a subpopulation of T lymphocytes, which leads to a different cell phenotype and results in immune protection or exacerbation of the disease. Leishmanias persist in the body both in asymptomatic infections and after treatment, representing risks in terms of immunosuppression. The objective of this study was to evaluate the effects of infection and immunosuppression by dexamethasone associated with pentoxifylline on animal weight, spleen weight, the parasitic load in the spleen and liver, as well as the production of IFN-gamma and IL-10 in spleen cell culture of Balb/c mice infected with Leishmania chagasi. The infection did not alter animal weight gain, but spleen weight and size increased. The immunosuppression, induced by dexamethasone associated with pentoxifylline, affected animal weight gain and weight and size of the spleen (in infected and not infected animals). The immunosuppression did not significantly alter the course of the parasite burden in the spleen and liver. Dexamethasone and pentoxifylline affected the studied cytokine production, but not influenced on Th1/Th2 response in infected animals.

Use of anaerobic cecal microflora, lactose and acetic acid for the protection of broiler chicks against experimental infection with Salmonella Typhimurium and Salmonella enteritidis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cell-mediated immune response to Leishmania chagasi experimental infection of BALB/c immunosuppressed mice

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Experimental infection of pregnant queens with two major Brazilian clonal lineages of Toxoplasma gondii

Toxoplasma gondii isolates from Brazil are biologically and genetically different from European and North America isolates. Recently, four genotypes were considered the common clonal lineages in Brazil and were designated as types BrI, BrII, BrIII, and BrIV. The pathogenicity of two major Brazilian lineages was investigated after oral inoculation of queens in the middle third of their pregnancies with T. gondii cysts. Twelve pregnant queens without T. gondii antibodies were distributed in group A (infected with a type BrI isolate); group 2 (infected with type BrIII isolate), and group 3 (non-infected control). Infection with type BrI isolate caused toxoplasmosis manifestations and abortion from one litter. Toxoplasmosis manifestations besides premature stillbirth of one litter were observed in queens infected with type BrIII isolate. Indirect fluorescence antibody test showed T. gondii antibodies in all eight infected queens at 30 days after inoculation. In two 10-day-old kittens of the same litter (group 1), titers of 16 and 64 were detected. At the same time, titers of 16, 32, and 32 were detected in three kittens from the same litter (group 2). Experimental infection with tissue cysts from a type BrI and type BrIII isolates of T. gondii developed similar reproductive disturbance in primary infected pregnant queens.

THE EFFECT OF CARBOHYDRATE ADMINISTRATION ON EXPERIMENTAL-INFECTION WITH SALMONELLA SEROTYPES IN CHICKENS

Carbohydrates and cultures of faecal microflora were administered to newly hatched chicks to prevent infection with Salmonella typhimurium Salmonella enteritidis, Salmonella agona and Salmonella infantis. Birds were killed 72 hours after challenge and the number of viable Salmonella organisms in their caecal contents estimated. Carbohydrates did not promote efficient control of infection with the Salmonella serotypes tested whereas cultures of faecal microflora completely prevented infection with all serotypes.

HAEMONCHUS PLACEI IN CALVES - EFFECTS OF DIETARY-PROTEIN AND MULTIPLE EXPERIMENTAL-INFECTION ON WORM ESTABLISHMENT AND PATHOGENESIS

An experiment was conducted to examine the influence of dietary protein and immunisation on parasite establishment and pathogenesis of Haemonchus placei in calves. Four groups of 4-6-month-old worm-free calves (n=4) were given a low protein diet (LP) containing 213 g crude protein (CP) per head per day or a high-protein diet (HP) containing 469 g per head per day CP. Five weeks later, calves in one of the two groups of each dietary treatment were given 50 000 H. placei infective larvae (L(3)). Twenty-five days later, infection in these groups was terminated by dosing with oxfendazole, This immunisation process was repeated 4 days later. Four days after termination of the second immunisation all calves were challenged with 100 000 L(3). Five weeks later, all calves were slaughtered for abomasal worm counts. Worm establishment was lower in the immunised groups; however, only the HP-I group showed a significant reduction (P < 0.05). All calves gained weight during the first 13 week period, and after challenge the non-immunised groups lost weight, independent of the level of protein in the diet (P < 0.05), Packed cell volume values for all treatments only dropped after challenge (P < 0.05) and the HP-immunised group presented values significantly higher when compared with the other treatments, All calves were hypoproteinaemic and hypoalbuminaemic at the end of the experiment, regardless of the treatment. Immunised calves showed a normocytic normochromic anaemia, while the non-immunised groups presented a microcytic normochromic anaemia.

Comparative susceptibility and pathogeny of Nelore and Holstein-Friesian calves to the experimental infection of Haemonchus placei (Place, 1893)

Two groups of Holstein-Friesian and Nelore calves, five animals each, about nine months old, received, by oral route, 1,000 infective larvae (L-3) per kg of body weight of Haemonchus placei. Blood samples were collected by venipuncture, at weekly intervals, from one week before, to eight weeks after infection. Hematological studies comprised the hematocrit, differential leukocyte counts, hemoglobin, fibrinogen and plasma protein determinations. Parasitological examinations covered weekly fecal egg counts (EPG) and worm burden counts at necropsy. Samples of the abomasal mucosa were submitted to gross examination and histopathological studies. Both groups had increasing EPG after the fifth week, with Holstein calves showing higher counts than the Nelore. Holstein calves had anemia and hipoproteinemia from the third week post-infection to the end of the experiment, whereas Nelore calves showed no significant differences in those, parameters. Holstein calves had significantly larger worm counts than the Nelore. The gross and histopathological lesions in the abomasum at necropsy were very similar, although macroscopically they look more apparent in the Holstein group. These results showed that Holstein calves are more susceptible to the infection and pathogenic effects of H. placei than Nelore calves.

Use of cecal microflora cultured under aerobic or anaerobic conditions in the control of experimental infection of chicks with Salmonella Enteritidis

One-day-old broiler chicks received cecal microflora (CM) cultured under aerobic, anaerobic conditions, or both (mixed) and were then infected with Salmonella Enteritidis, in order to compare the efficacy of these different types of culture in terms of the number of chicks infected, cecal colonization and faecal excretion of the challenging bacteria. Regardless of culture type, CM always led to a smaller number of S. Enteritidis for any of the parameters studied compared to untreated chicks. Aerobic CM demonstrated better efficacy in reducing the number of infected chicks and cecal colonization by S. Enteritidis, followed by mixed CM. No difference was observed in faecal excretion of S. Enteritidis between the chicks that received different types of CM culture. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Experimental infection of bovines with oocysts of Toxoplasma gondii

Calves aged 3 mth were readily infected with oocysts and cysts of Toxoplasma gondii administered by the oral route. Fever, respiratory distress, nasal discharge, and hyperemia of the conjunctivas were the most significant clinical signs noted in the infected animals. Parasitemia was demonstrated in all infected calves. It occurred on different days and up to 62 days after the infection. Toxoplasma was demonstrated in tissues of all infected calves, and the organ most frequently parasitized was the lymph node. Parasitism of the retina was demonstrated in 2 calves. All infected animals had antibody against T. gondii in their serum. The Sabin-Feldman dye test and the indirect immunofluorescent test were both useful in detecting antitoxoplasma antibody.