Kinetics of serum antibody responses in broiler chicks againstCryptosporidium baileyi

Microbiota-produced indole metabolites disrupt mitochondrial function and inhibit Cryptosporidium parvum growth

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children in resource-poor settings. To explore microbial influences on susceptibility, we screened 85 microbiota-associated metabolites for their effects on Cryptosporidium parvum growth in vitro. We identify eight inhibitory metabolites in three main classes: secondary bile salts/acids, a vitamin B6 precursor, and indoles. Growth restriction of C. parvum by indoles does not depend on the host aryl hydrocarbon receptor (AhR) pathway. Instead, treatment impairs host mitochondrial function and reduces total cellular ATP, as well as directly reducing the membrane potential in the parasite mitosome, a degenerate mitochondria. Oral administration of indoles, or reconstitution of the gut microbiota with indole-producing bacteria, delays life cycle progression of the parasite in vitro and reduces the severity of C. parvum infection in mice. Collectively, these findings indicate that microbiota metabolites impair mitochondrial function and contribute to colonization resistance to Cryptosporidium infection.

Microbiota produced indole metabolites disrupt host cell mitochondrial energy production and inhibit Cryptosporidium parvum growth

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children in resource-poor settings. Susceptibility rapidly declines with age, associated with changes in the microbiota. To explore microbial influences on susceptibility, we screened 85 microbiota- associated metabolites enriched in the adult gut for their effects on C. parvum growth in vitro. We identified eight inhibitory metabolites in three main classes: secondary bile salts/acids, a vitamin B 6 precursor, and indoles. Growth restriction of C. parvum by indoles did not depend on the host aryl hydrocarbon receptor (AhR) pathway. Instead, treatment impaired host mitochondrial function and reduced total cellular ATP, as well as directly reduced the membrane potential in the parasite mitosome, a degenerate mitochondria. Oral administration of indoles, or reconstitution of the gut microbiota with indole producing bacteria, delayed life cycle progression of the parasite in vitro and reduced severity of C. parvum infection in mice. Collectively, these findings indicate that microbiota metabolites contribute to colonization resistance to Cryptosporidium infection.

The dynamics of antibody response to Escherichia coli vaccination in meat-type chicks

The dynamics of serum antibody (Ab) response in young broilers were studied in lines divergently selected for high (HC) or low (LC) Ab response to Escherichia coli vaccination at an early age, and their cross (HL). Chicks were divided into three vaccination-age (VA) groups: 8, 10, and 12 d of age (VA8, VA10, and VA12, respectively). Antibody response was determined five times for each chick, at 6, 8, 10, 12, and 14 d postvaccination (dPV). The effects of line, VA, and dPV on Ab titers were highly significant. The HC and LC chicks exhibited the highest and lowest mean titers, respectively, in all VA groups. The HL chicks exhibited midparent Ab values for all VA and dPV combinations, indicating additive inheritance of early Ab production. In LC, the highest mean Ab titer was obtained on Day 26 (14 dPV of the VA12 group), whereas in HC, the same titer had already been obtained on Day 18 (VA8-10 dPV and VA10-8 dPV combinations). The VA8 and VA12 chicks differed markedly in their Ab titer dynamics curves, and the VA10 chicks exhibited an intermediate curve. The three VA groups exhibited a similar change in Ab level from 6 to 10 dPV, but they differed in Ab change from 10 to 14 dPV. This significant dPV x VA interaction suggests that the VA12 and VA10, but not VA8, chicks maintained the capability to produce persisting Ab.

Influence of in ovo administered Cryptosporidium baileyi oocyst extract on the course of homologous infection

In order to evaluate the effect of in ovo vaccination on avian cryptosporidiosis, two doses (1 and 10microg) of Cryptosporidium baileyi oocyst extract (OE) were injected into the amnionic sac of embryonated, specific pathogen-free chicken eggs. After hatching these birds as well as infected controls (IC) were inoculated with 8x10(5) C. baileyi oocysts at 10 days of age. Another group of chickens remained uninfected (UC). Faecal oocyst shedding was measured every second day, and weekly ELISAs were performed to monitor seroconversion. Those chickens that received OE during embryogenesis showed dose-dependent shift in their oocyst shedding, with higher oocyst output of OE1 and OE10 birds compared to IC ones. The patency was significantly longer in the OE10 group than in IC or OE1. ELISA results showed low seroconversion of OE1 and OE10 chickens prior to homologous challenge. Challenge infection resulted in antibody levels without significant difference between IC, OE1 and OE10 groups. These data suggest that in ovo vaccination with C. baileyi oocyst extract does not promote immune response, moreover, it may impair immunity and thus delay the clearance of cryptosporidia from chickens.

Cryptosporidiosis in birds--a review

The morphology, life cycle, maintenance, host specificity, incidence of Cryptosporidium species infecting birds, as well as the epidemiology, clinical signs, pathology, immunology, diagnosis, therapy, and control of avian cryptosporidiosis are reviewed. Based on the accepted criteria used for differentiation of Cryptosporidium isolates into valid species, this review places the validity of C. meleagridis in doubt and suggests that C. meleagridis isolated from birds is very closely related to, or identical with C. parvum infecting more than 100 species of mammals.

Interaction of chicken anaemia virus and Cryptosporidium baileyi in experimentally infected chickens

The natural occurrence of concomitant chicken anaemia virus (CAV) and Cryptosporidium baileyi infection was described earlier. In this experiment, 1-day-old chickens were infected with CAV alone (anaemia virus infected, AI) or followed by inoculation with 8 x 10(5) C. baileyi oocysts orally at 1 wk of age (anaemia virus and Cryptosporidium infected, ACI). Another group of chickens received the same dose of C. baileyi oocysts without previous virus infection (Cryptosporidium infected, CI), and two groups of uninfected chickens served as controls. Except one group (uninfected control, UC), all groups -- including the other control group (challenged control, CC) -- were challenged with an oral inoculum of 8 x 10(5) C. baileyi oocysts at the age of 4 wk. Haematological, serological, immunohistochemical and pathological findings confirmed the effect of the virus agent. The individual C. baileyi oocyst shedding did not show significant difference between group CI and ACI, however, after challenge infection the AI chickens shed approximately three times more C. baileyi oocysts than those in group CC. Mortality and the percentage of birds that developed anaemia was significantly higher among ACI than AI chickens, while haematocrit values at 2 wk of age and relative bursal weights at 4 wk of age were moderately lower in the ACI group. The results presented here suggest that concurrent CAV infection increases the reproductive potential of C. baileyi in chickens, and both pathogens have synergistic effect on each other.

Effect of F-2 and T-2 fusariotoxins on experimental Cryptosporidium baileyi infection in chickens

The course of Cryptosporidium baileyi infection in chickens fed with different doses of fusariotoxins was compared with that of control groups. F-2 toxin levels of 0.187-1.5 mg kg-1 and T-2 toxin levels of 0.187-6.0 mg kg-1 were investigated. The experimental animals were orally infected with 6 x 10(5) C. baileyi oocysts at 1 week of age. Total daily oocyst output was monitored by a quantitative method. Acquired immunity was tested at the age of 4 weeks, by ELISA and by a challenge infection with an equal number of oocysts, upon recovery from the primary infection. The results show that in chickens kept on the lower doses of F-2 and T-2 toxins, the parasite infection ran a similar course to that in the control groups, and the animals became resistant to re-infection. However, when higher doses (2.0-6.0 mg kg-1) of T-2 toxin were used, a depression of weight gain was observed with some other physiological parameters (PCV, weight of bursa, weight of thymus, skin thickness in PHA-P skin test) also indicating toxic effect and, simultaneously, the oocyst output decreased significantly and the patent period was slightly prolonged. Although certain modifications of the immune response could be revealed, the chickens became resistant to re-infection. Only early (1 week of age) parasite infection and 6 mg kg-1 T-2 toxin in the feed significantly depressed body weight gain and immunity.