Effect of Cryptosporidium baileyi on broilers infected at 26 days of age

Cryptosporidium baileyi causes respiratory disease, pallor, death, and transient increased feed conversion (FC) and decreased body weight gain (BWG) when intratracheally (IT) inoculated into young chicks. Unlike the case for young chicks in previous studies, C. baileyi had no effect on FC, BWG, or mortality in IT-inoculated 26-day-old chicks. Results from two different histologic evaluations indicated that IT inoculation with 10(4) oocysts caused higher epithelium lesion scores (P less than 0.05) and higher mucosal area scores (P less than 0.05) than did IT inoculation with more, fewer, or no oocysts. Reasons for these findings and implications of chicken immune system response to or modulation by C. baileyi are discussed.     

Interaction of reovirus and Cryptosporidium baileyi in experimentally infected chickens

No clinical signs, gross lesions, or increased mortality were observed in specific-pathogen-free chickens orally inoculated at 5 days of age with Cryptosporidium baileyi, reovirus 2035, reovirus 2408, or combinations of these agents. Weight gain of chickens inoculated with only reovirus 2408 was depressed 0-8 days postinoculation (PI) (P less than 0.01) but not for the 21-day period PI. Weight gain of chickens inoculated with only reovirus 2035 was not affected. Cryptosporidium baileyi infection significantly depressed weight gain 8-14 days PI but not for the entire 21-day period PI. Weight gain of chickens infected with both C. baileyi and reovirus 2035 was significantly depressed 0-14 days PI and for the entire 21-day period PI. Dual infection with C. baileyi and either reovirus appeared to promote shedding of both agents. Cryptosporidia were found principally in the rectum 2-10 days PI and in the bursa of Fabricius 6-10 days PI. Reovirus infection did not cause any microscopic lesions and did not modify lesions caused by C. baileyi infection.     

Performance and oocyst shedding in broiler chickens orally infected with Cryptosporidium baileyi and Cryptosporidium meleagridis

To study effects of experimental cryptosporidiosis, broiler chickens were infected per os with 5 x 10(5) oocysts of Cryptosporidium baileyi and Cryptosporidium meleagridis. In the first experiment, chickens were infected with oocysts of C. baileyi at the age of 7, 14, and 21 days. In the second experiment, chickens were infected with oocysts of C. baileyi, C. meleagridis, or both cryptosporidial species at the age of 7 days. Although clinical signs of infection were apparent, neither final live weight nor mortality was significanty influenced in chickens infected with a single Cryptosporidium species. In chickens infected with C. meleagridis, the growth retardation was observed in the 2-wk period after infection. The compensatory growth, however, started when the oocyst shedding had ceased. The number of oocysts in excreta specimens of chickens infected with C. meleagridis was two to three times lower than in excreta of chickens infected with C. baileyi. Chickens infected with both C. baileyi and C. meleagridis (5 x 10(5) oocysts of each) had significantly lower final live weight and worse feed efficiency than chickens of other groups. Concurrent infection did not influence individual C. baileyi or C. meleagridis oocyst shedding.     

2株贝氏隐孢子虫鸡源分离株对雏鸡的致病性比较

为了解不同地区鸡源贝氏隐孢子虫的致病特点,对收集到的郑州、林州两地区鸡源贝氏隐孢子虫卵囊经雏鸡传代扩增纯化后,分别以1×106个卵囊量接种3日龄罗曼公雏鸡,从其排卵囊情况、临床症状和病理学变化比较了2个分离株的致病情况。结果表明:2个隐孢子虫分离株均主要引起雏鸡呼吸道症状和法氏囊炎病变;接种雏鸡均于感染后第4天开始排卵囊,林州株和郑州株排卵囊持续期分别为23 d和13 d;排卵囊高峰期均为感染后第8~12天。雏鸡感染2个地区鸡源贝氏隐孢子虫分离株后,排卵囊量及排卵囊规律存在差异。     

Interaction of Marek's disease virus and Cryptosporidium baileyi in experimentally infected chickens

Histocompatible B13/B13 white specific-pathogen-free leghorn chickens were used to investigate the effect of coinfection with Cryptosporidium baileyi and the HPRS 16 strain of Marek's disease virus (MDV) in chickens and to assess the pathogenicity of C. baileyi when MDV is given before or after the parasite. Groups of chickens concurrently infected with C. baileyi orally inoculated at day (D)4 and MDV inoculated at hatching (C4M0 group) or at D8 (C4M8 group) were compared with relevant control groups inoculated with only C. baileyi at D4 (C4 group), only MDV at hatching (M0 group) or at D8 (M8 group), and an uninoculated control group (UC group). The chickens were kept in isolator units until the end of the experiment at D62. Our results showed a considerable synergistic effect in concurrently infected chickens and more severe consequences when chickens received MDV before C. baileyi infection. In fact, except for a slight transitory weakness, the chickens in C4 group remained free of overt clinical signs and there was no mortality. However, coinfection with both pathogens induced more lasting or permanent oocyst shedding. Severe clinical cryptosporidiosis with weakness, anorexia, depression, growth retardation, and chronic and severe respiratory disease causing death occurred in all chickens in the C4M0 group between D12 and D43 and in 67% of the chickens in the C4M8 group between D17 and D57. Eighty-two percent and 33%, respectively, died before the development of specific Marek's disease lesions. Mortality rates were 27% and 33% in the M0 and M8 groups, respectively. The presence of MDV enhanced the establishment of more lasting cryptosporidial infection in the respiratory tract, esophagus, crop, proventriculus, and kidneys (only in C4M0 group) as well as in bursa of Fabricius, ceca, and cloaca. Serologic analysis showed that chickens with chronic cryptosporidiosis in the C4M8 group had an increased level of C. baileyi-specific immunoglobulin A. Our results may explain some cases of mortality in chickens naturally infected with MDV and Cryptosporidium.     

不同禽源贝氏隐孢子虫分离株对雏鸡致病性比较研究

为研究不同禽源贝氏隐孢子虫对雏鸡的致病性差异,人工感染3日龄雏鸡鸡源、鸭源、鹌鹑源、白文鸟源贝氏隐孢子虫.结果发现,各感染组雏鸡潜隐期均为4d,显露期为11～18 d,均未发生死亡,但其增重均受影响.鸡源C.baileyi(林州株)、C.baileyi(郑州株)和鸭源C.bailey(郑州株)感染组雏鸡临床症状较为明显,发病率较高,分别为71.4％、85.7％和77.1％,剖检可见气管有较多粘液分泌物,法氏囊粘膜充血肿胀,平均增重较不感染对照组分别减少34.5、53.1和19.7 g；鹌鹑源C.bailey(武陟株)和白文鸟源C.bailey(郑州株)感染组雏鸡仅部分表现轻微临床症状,发病率分别为31.4％和28.6％,平均增重较不感染对照组分别减少39.7和43.1g.结果表明不同禽源C.bailey对雏鸡均有不同程度的致病性,以鸡源和鸭源C.baileyi致病性较强.     

鸭源贝氏隐孢子虫对鸡的致病性

设计3个不同剂量的鸭源隐孢子虫试验感染2日龄雏鸡,通过临床症状、增重、排卵囊规律和法氏囊指数及寄生器官组织扫描电镜观察,证实贝氏隐孢子虫160万个卵囊感染即可引起明显的呼吸道症状,发病鸡增重显著降低,法氏囊严重萎缩。贝氏隐孢子虫致病程度和排卵囊规律与感染剂量相关,主要病变表现呼吸道病变和法氏囊炎症。     

Experimentally induced infections in turkeys with Cryptosporidium baileyi isolated from chickens

Oocysts of Cryptosporidium baileyi isolated from chickens were inoculated by different routes into 3 groups of turkey poults. Intratracheal inoculation of oocysts produced clinical signs of respiratory tract disease, deaths, and gross lesions of airsacculitis. Parasites developed in the microvillous border of the nasopharynx, larynx, trachea, bronchi, and air sacs. Oral and intracloacal inoculations of oocysts caused no deaths or clinical signs of disease, but did produce patent infections. Respiratory tract infections limited to the nasopharynx, larynx, and trachea occurred in 3 orally inoculated poults. Respiratory tract infections were not observed in intracloacally inoculated poults. The mode of inoculation did not influence the distribution of C baileyi in the digestive tract. The cloaca was parasitized in 100% of the birds with intestinal infections, and the bursa of Fabricius was parasitized in 72.7%.     

Renal Cryptosporidiosis (Cryptosporidium baileyi) in specific-pathogen-free chickens experimentally coinfected with Marek's disease virus

Renal Cryptosporidiosis was experimentally induced during a study to investigate the pathogenicity of Cryptosporidium baileyi in specific-pathogen-free (SPF) chickens coinfected with Marek's disease virus (MDV). Cryptosporidium baileyi was administered orally at 4 days of age to chickens previously infected at hatching (day 0) with the HPRS 16 strain of oncogenic MDV. Three control groups received MDV at hatching, C. baileyi on day 4, or placebo consisting of distilled water. Renal cryptosporidiosis lesions were induced in the group coinfected with MDV and C. baileyi. The kidneys were markedly swollen and pale, with visible urate crystals in the ureters and surface tubules. Oocysts of C. baileyi were demonstrated in six of seven cases tested by a scoring method with modified Sheather's sugar solution on renal tissue scrapings and were confirmed in three cases by histologic examination of paraffin-embedded kidney sections. Histologic study also revealed subacute interstitial nephritis, acute ureteritis, and attachment of cryptosporidia on the epithelial cell surface of the ureters and collecting ducts, collecting tubules, and distal convoluted tubules. Various developmental stages of the parasite were present in the kidney sections. To our knowledge, this is the first report of experimentally induced renal cryptosporidiosis in SPF chickens coinfected with MDV.     

Molecular study and genotyping of Cryptosporidium baileyi and Cryptosporidium parvum from free-range and commercial broiler chickens in Guilan province,Iran

Cryptosporidiosis acutely impacts the digestive and/or respiratory tract of the birds in many species of various orders. More importantly, it is also well known as a significant zoonotic disease, which can lead to diarrhea in humans and livestock. Regarding increasing demand for free-range products and increasing the number of free-range poultry farms, the present paper evaluated histopathological and molecular detection of Cryptosporidium baileyi and Cryptosporidium parvum in free-range and commercial broiler chickens in the north part of Iran. For this purpose, 100 fecal and tissue samples of the chickens in Guilan province were collected. After microscopic examination using Ziehl-Neelsen staining, molecular analyses of the fecal samples were processed by Nested-PCR targeting the 18S rRNA gene followed by sequencing of the amplicons and phylogenetic analyses. Eventually, the tissue samples were studied for histological lesions. Findings demonstrated the presence of Cryptosporidium baileyi and Cryptosporidium parvum in 6 % and 2 % of fecal samples, respectively. This is the first identification of C.parvum in avian hosts in Iran, and for the first time, C.baileyi and C.parvum are shown in native free-range chickens in Iran. All of the PCR positive birds with clinical symptoms showed gross lesions of respiratory infections. There was no significant difference between infection rate in free-range and commercial broiler chickens; however, the infection rate was significantly higher in chickens <25 days old. To conclude, we present here a notable Cryptosporidium infection rate in the free-range chicks in Iran, which notify the role of this host as a reservoir and should be more noted due to the economic and zoonotic importance.     

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.     

Effects of colostral antibody on susceptibility of calves to Cryptosporidium parvum infection

Effects of colostral antibody on susceptibility of calves to Cryptosporidium parvum infection were examined. Six calves were fed pooled colostrum that contained C parvum antibody, 6 times daily (at 4-hour intervals) for 7 days and then milk replacer for 7 days. Colostrum was obtained from healthy cows or cows inoculated parenterally with C parvum oocysts before parturition. Antibody content was determined in serum and colostrum whey, using an ELISA for anticryptosporidia immunoglobulin. Six calves were fed colostrum from healthy cows 1 time, and then milk replacer 6 times daily for 14 days. On day 1, all calves were challenge exposed with C parvum, PO, and were monitored daily for diarrhea and oocyst shedding. Bovine colostrum containing specific antibody to C parvum, at ELISA titers up to 10,240, was not effective in protecting calves against challenge exposure to C parvum.     

Effect of acidified feed on susceptibility of broiler chickens to intestinal infection by Campylobacter and Salmonella

Consumption of poultry meat is associated with human Campylobacter and Salmonella infections. One way to control the presence of these bacteria in broiler flocks is to make chickens less susceptible for colonisation. Acidification of feed may be a tool to reduce the Campylobacter and Salmonella carriage in broiler chickens. In the present experiments an acidified feed with high levels of organic acid, 5.7% lactic acid and 0.7% acetic acid, was applied. In an in vitro experiment the reduction or growth of Campylobacter and Salmonella was measured after addition of 10(7)cfu of these bacteria into a conventional broiler feed, acidified feed and fermented feed, whereas the numbers of Salmonella increased in non-acidified feed. The number of Campylobacter decreased 2-3 (10)log cfu. In the acidified and fermented feed a complete reduction of Campylobacter was observed within 20 min, and a total Salmonella reduction started after 1h, and was complete after 2h. Subsequently, an in vivo experiment with 100 individually housed broiler chickens showed that chickens fed acidified feed were less susceptible to an infection with Campylobacter than were chickens fed conventional feed. The size of reduction was however limited. The susceptibility for Salmonella colonisation was not affected by acidified feed. It is concluded that the role for acidified feed in the control of Campylobacter and Salmonella is limited.     

Cryptosporidium baileyi: effects of intra-abdominal and intravenous inoculation of oocysts on infectivity and site of development in broiler chickens

Developmental stages of Cryptosporidium baileyi were observed on the epithelium of the larynx, trachea, primary and secondary bronchi, air sacs, bursa of Fabricius, and cloaca of 12 chickens inoculated intra-abdominally with oocysts. All 12 birds inoculated intra-abdominally developed clinical signs of respiratory disease and had gross lesions of airsacculitis at necropsy. Developmental stages of C. baileyi and clinical signs of disease were not observed in 12 chickens inoculated intravenously with oocysts. The response of chickens to intra-abdominal inoculation of oocysts was similar to responses recorded following intratracheal inoculation of oocysts in previous studies.     

Study on the course of Cryptosporidium baileyi infection in chickens treated with interleukin-1 or indomethacin.

The effects exerted by human recombinant interleukin-1 beta (hrIL-1 beta) and the prostaglandin inhibitor indomethacin on the course of Cryptosporidium baileyi infection in chickens were studied. Daily oocyst shedding was monitored by a quantitative method throughout the experiment. Humoral immune response to C. baileyi was assessed by ELISA at 3 weeks of age while the level of cellular immune response to phytohaemagglutinin-P (PHA-P) by a skin test at 23 days of age. Parenteral application of hrIL-1 beta decreased oocyst shedding to 62%, but the infection ran a similar course in treated and control birds. The PHA-P skin test demonstrated increased cellular immune reaction in chickens receiving IL-1 beta, but there was no significant difference in the humoral responses of the two groups as detected by ELISA. On the other hand, indomethacin mixed to the feed lessened oocyst shedding to 13.7% and also shortened its duration. Immunological parameters as reflected by PHA-P skin test and ELISA results indicated enhanced cellular but unaltered humoral immune response. These data suggest that the systemic application of interleukin-1 can induce partial protection against C. baileyi in chickens and that prolonged, abundant oocyst shedding is due to an indomethacin-sensitive immunodepression via the prostaglandin pathway.     

Pulse and continuous oral norfloxacin treatment of experimentally induced Escherichia coli infection in broiler chicks and turkey poults

Experimental colibacillosis was produced in 40 healthy, 7-day-old broiler chickens and turkeys by intratracheal injection of 1 x 10(8) CFU/chick and 1.23 x 10(9) CFU/poult bacteria of an O1:F11 strain of Escherichia coli, respectively. Two days before E. coli challenge all chicks were vaccinated with a live attenuated strain of infectious bronchitis virus (H-52). This model of infection--at least in chicken--proved to be useful for evaluating the efficacy of antimicrobial medication, by recording mortality, body weight gain, pathological alterations and frequency of reisolation of E. coli. Using this model, the efficacy of two different dosing methods of norfloxacin (continuous and pulse dosing) was evaluated. The once-per-day pulse dosing of norfloxacin administered via the drinking water at 15 mg/kg body weight proved to be more efficacious than the continuous dosing method of 100 mg/L for 5 days in chickens, while there were no convincing differences between the two treatment regimens in turkeys. The results confirmed earlier observations on the pharmacokinetic properties of norfloxacin in chicks and turkeys (Laczay et al., 1998).     

Effect of intramammary infusion of bacterial lipopolysaccharide on experimentally induced Staphylococcus aureus intramammary infection

Mastitis due to Staphylococcus aureus is a significant problem in the dairy industry and is refractory to antibiotic treatment and/or vaccine prevention. Relative to other mastitis-causing pathogens, S. aureus elicits a diminutive host inflammatory response during intramammary infection. To determine whether induction of a heightened inflammatory response could influence outcome of infection, the highly pro-inflammatory molecule bacterial lipopolysaccharide (LPS) was infused into udder quarters experimentally infected with S. aureus. Relative to S. aureus-infected udder quarters receiving saline, quarters infused with LPS demonstrated a heightened inflammatory response as demonstrated by the induction of TNF-alpha and higher milk somatic cell counts and albumin levels. Although there was no overall effect on bacterial clearance, a trend toward reduced bacterial numbers during the immediate pro-inflammatory response following LPS infusion was observed suggesting that this novel approach to treating S. aureus intramammary infection may warrant further investigation.     

Effects of dietary tannic acid and vaccination on the course of coccidiosis in experimentally challenged broiler chicken

An experiment was carried out to assess the influence of tannic acid (TA) on integrity of the intestine in broiler chicks vaccinated against coccidiosis and challenged with the disease. In a 2 × 2 factorial design, the trial had five groups of 10 chickens each, including positive (group 2) and negative (group 1) controls. The chickens were kept on wood shavings and fed a commercial maize and soybean-based starter-grower diet. From day 1, groups 3 and 5 received TA (10 g kg(-1)) in their diet. On day 4, birds of groups 4 and 5 were vaccinated orally against coccidiosis with anti-coccidial vaccine, Livacox T?. Each dose of the vaccine contained 300-500 sporulated oocysts of each of Eimeria acervulina, Eimeria maxima and Eimeria tenella. On day 18, all experimental groups except for the negative (group 1) were challenged with 10-fold dose of Livacox T? to produce a mild coccidiosis infection. Faecal samples of individual birds were collected on day 23, and the number of faecal oocysts was determined. d-Xylose absorption test was also carried out on all birds on day 23. Immediately after d-xylose absorption test, all birds were killed humanely and the intestinal tract was removed, weighed and examined for gross lesions. Results showed that negative (group 1) and positive controls (group 2) had the highest and lowest levels of plasma d-xylose post-ingestion of the substrate, respectively. Vaccination and/or feeding TA raised the level of plasma d-xylose in infected birds, although this was not significant for TA-fed birds. Vaccination reduced but TA increased the total number of oocysts per gram of faeces. Birds of groups 2-5 had distinct intestinal lesions when compared with group 1. However, vaccination prevented intestinal lesions. Relative weights of intestinal parts were the lowest in group 1 and the highest in group 2. Vaccination but not TA reduced the relative weights of intestinal parts in infected birds. It was concluded that dietary tannins may reduce the efficacy of anticoccidial vaccines and alter the proper development of immunity against the disease.     

木聚糖酶对肉仔鸡生产性能的影响

768羽1日龄AA肉仔鸡,随机分为6个处理,每个处理分8个重复,每个重复16羽肉仔鸡(公母各半)。6个处理分别为玉米-豆粕型日粮添加木聚糖酶0和1000IU/kg处理组,小麦-玉米-豆粕型日粮添加木聚糖酶0,500,1000和1500IU/kg处理组。试验采用4层立体网上养殖(使用上面3层),饲养周期为1～6周龄(前期和中期)。研究玉米和小麦基础日粮中单独使用木聚糖酶对肉仔鸡生产性能的影响。结果表明:玉米-豆粕型日粮中添加1000IU/kg的木聚糖酶对肉仔鸡前期和后期的生长性能无显著影响(P>0.05),但有改善的趋势;小麦-玉米-豆粕型日粮中添加木聚糖酶提高了肉仔鸡的采食量,改善了肉仔鸡的饲料转化效率(P<0.05);小麦-玉米-豆粕型日粮中3个木聚糖酶添加水平之间对肉仔鸡生产性能无显著影响,同样对肠道食糜黏度无影响,提示在本研究条件下500IU/kg木聚糖酶能满足分解木聚糖的需要;尽管小麦-玉米-豆粕型添加木聚糖酶改善了动物生产性能,但仍显著低于玉米-豆粕型日粮,提示在生产实践中单独添加一种酶的作用是有限的。