Molecular prevalence and characterization of Cryptosporidium in domestic free-range poultry in Anhui Province, China

The risk of wild birds contaminating source water with zoonotic Cryptosporidium and Giardia is probably overestimated

Cryptosporidium and Giardia are important waterborne protozoan parasites that are resistant to disinfectants commonly used for drinking water. Wild birds, especially wild migratory birds, are often implicated in the contamination of source and wastewater with zoonotic diseases, due to their abundance near water and in urban areas and their ability to spread enteric pathogens over long distances. This review summarises the diversity of Cryptosporidium and Giardia in birds, with a focus on zoonotic species, particularly in wild and migratory birds, which is critical for understanding zoonotic risks. The analysis revealed that both avian-adapted and zoonotic Cryptosporidium species have been identified in birds but that avian-adapted Cryptosporidium species dominate in wild migratory birds. Few studies have examined Giardia species and assemblages in birds, but the non-zoonotic Giardia psittaci and Giardia ardeae are the most commonly reported species. The identification of zoonotic Cryptosporidium and Giardia in birds, particularly C. parvum and G. duodenalis assemblages A and B in wild migratory birds, is likely due to mechanical carriage or spillback from birds co-grazing pastures contaminated with C. parvum from livestock. Therefore, the role of wild migratory birds in the transmission of zoonotic Cryptosporidium and Giardia to source water is likely overestimated. To address knowledge gaps, it is important to conduct more extensive studies on the prevalence of Cryptosporidium and Giardia in a broader range of migratory wild birds. There is also a need to investigate the extent to which zoonotic infections with C. hominis/C. parvum and G. duodenalis assemblages A and B are mechanical and/or transient, and to assess the load and viability of zoonotic oo/cysts shed in avian faeces. Understanding the contribution of birds to zoonoses is essential for effective disease surveillance, prevention, and control.

Dominant infection of Cryptosporidium baileyi in broiler chickens in Zhejiang Province, China

Cryptosporidium is a common enteric parasite in chickens. A total of 812 fecal specimens were collected from 11 broiler farms in Zhejiang Province, China, and analyzed by nested PCR amplification based on the small subunit ribosomal RNA (SSU rRNA) gene. The overall infection rate of Cryptosporidium was 6.3% (51/812), and five of 11 farms were Cryptosporidium positive. Broilers aged > 90 days accounted for the highest infection rate of 16.1% (6/56), followed by those aged 30-60 days (10.6%, 38/358) and 60-90 days (4/378, 1.1%). Two Cryptosporidium species were identified by sequence analysis, with the predominant species being C. baileyi (96.1%, 49/51) and the minor infection being C. meleagridis (3.9%, 2/51). Based on the 60-kDa glycoprotein (gp60) gene, two C. meleagridis-positive isolates were identified as one known subtype, IIIbA24G1R1. This study indicated the common occurrence of C. baileyi in broiler chickens in this region and low zoonotic transmission potential of Cryptosporidium to humans.

Longitudinal surveillance of Cryptosporidium spp. in broiler chickens in Xinjiang, northwest China: genetic diversity of Cryptosporidium meleagridis subtypes

Cryptosporidium spp. are common enteric parasites in humans and animals. Herein, 175 faecal specimens were collected from a broiler farm in Xinjiang, China, including seven repeated samplings at 10-day intervals of broilers aged 10 to 70 days. Cryptosporidium was detected and identified by PCR-RFLP analysis. The overall infection rate of Cryptosporidium in broilers was 23.4% (41/175), with the highest infection rate of 48.0% (12/25) at 40 days of age, and no infection was detected at 10 days of age. Two Cryptosporidium species were confirmed, namely, C. baileyi (3.4%, 6/175) and C. meleagridis (20%, 35/175). In total, 21 of 35 C. meleagridis isolates were successfully subtyped based on the gp60 gene, and one known subtype, IIIgA22G3R1 (n = 1), and three novel subtypes, IIIbA25G1R1 (n = 10), IIIgA24G3R1 (n = 9) and IIIgA25G2R1 (n = 1), were identified. Our findings highlight the genetic diversity of C. meleagridis in Xinjiang and the potential endemic characteristics of the subtypes.

Molecular prevalence of Tetratrichomonas gallinarum and Trichomonas gallinae in three domestic free-range poultry breeds in Anhui Province, China

Tetratrichomonas gallinarum and Trichomonas gallinae can colonize the alimentary tract of domestic birds. However, little information is available on the epidemiology of the two trichomonad species in domestic free-range poultry in China. In this study, the occurrence and genetic characteristic of T. gallinarum and T. gallinae among free-range chickens, ducks, and geese in Anhui Province, China, were investigated. The 1910 fecal samples collected from 18 free-range poultry farms throughout Anhui Province were examined for the presence of T. gallinarum and T. gallinae by PCR and sequence analysis of the small subunit (SSU) rRNA gene of T. gallinarum and ITS1-5.8S-ITS2 sequence of T. gallinae. The overall occurrence of T. gallinarum in poultry was 1.2% (22/1910), with infection rates of 2.1% (17/829) in chickens, 0.2% (1/487) in ducks, and 0.7% (4/594) in geese. The constructed phylogeny tree using the concatenated ITS1-5.8S-ITS2 region and SSU rRNA indicated the T. gallinarum isolates detected in this study were closely related to previously defined genogroups A, D, and E, respectively. Nine (0.5%) fecal samples were positive for T. gallinae, with infection rates of 0.8% (7/829) in chickens, 0.4% (2/487) in ducks, and 0% (0/594) in geese. Sequence and phylogenetic analysis showed that four T. gallinae ITS1-5.8S-ITS2 sequences obtained from chicken feces and one duck fecal sample belonged to genotype ITS-OBT-Tg-1. This is the first report of the prevalence and genetic characterization of T. gallinarum and T. gallinae in free-range chickens, ducks, and geese in China.

Dominance of the zoonotic pathogen Cryptosporidium meleagridis in broiler chickens in Guangdong, China, reveals evidence of cross-transmission

Background

Cryptosporidium is one of the most prevalent parasites infecting both birds and mammals. To examine the prevalence of Cryptosporidium species and evaluate the public health significance of domestic chickens in Guangdong Province, southern China, we analyzed 1001 fecal samples from 43 intensive broiler chicken farms across six distinct geographical regions.

Methods

Individual DNA samples were subjected to nested PCR-based amplification and sequencing of the small subunit of the nuclear ribosomal RNA gene (SSU rRNA). Analysis of the 60 kDa glycoprotein gene (gp60) was performed to characterize the subtypes of C. meleagridis.

Results

The overall prevalence of Cryptosporidium was 13.2% (95% CI 11.1–15.3) (24 of 43 farms), with C. meleagridis (7.8%), C. baileyi (4.8%) and mixed infections (0.6%). Using the gp60 gene, three subtype families, IIIb, IIIe and IIIg, were identified, including six subtypes: one novel (IIIgA25G3R1a) and five previously reported (IIIbA23G1R1c, IIIbA24G1R1, IIIbA21G1R1a, IIIeA17G2R1 and IIIeA26G2R1). Within these subtypes, five known subtypes were genetically identical to those identified in humans.

Conclusions

This is the first report of C. meleagridis in chickens from Guangdong. The frequent occurrence of C. meleagridis in domestic chickens and the common C. meleagridis subtypes identified in both humans and chickens is of public health significance. Our study indicates that broiler chickens represent a potential zoonotic risk for the transmission of Cryptosporidium in this region.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05267-x.

Validation of a one-tube nested real-time PCR assay for the detection of Cryptosporidium spp. in avian fecal samples

The aim of this study was to validate a one-tube nested real-time PCR assay followed by genetic sequencing to detect and identify Cryptosporidium species and genotypes in birds. A total of 443 genomic DNA extracted from avian fecal samples were analyzed by one-tube nested real-time PCR and conventional nested PCR. By one-tube nested real-time PCR, 90/443 (20.3%) samples were positive for Cryptosporidium spp. In contrast, 36/443 (8.1%) samples were positive for Cryptosporidium spp. by conventional nested PCR. The analytical sensitivity test showed that one-tube nested real-time PCR detects approximately 0.5 oocyst (2 sporozoites) per reaction. An evaluation of analytical specificity did not reveal amplification of microorganisms that commonly present nonspecific amplification with primers used for the diagnosis of Cryptosporidium spp. The repeatability analysis showed the same result in 27 out of 30 samples (90%). As for the reproducibility of one-tube nested real-time PCR, 24 of the 30 samples examined (80%) showed the same result. All the 90 samples amplified by one-tube real-time nested PCR were successfully sequenced, leading to the identification of C. baileyi, C. galli, C. meleagridis, C. proventriculi, and Cryptosporidium avian genotype I. Genetic sequencing of conventional nested PCR amplicons was successful in 10/36 (27.8%) of positive samples.

Genetic characterization of Cryptosporidium spp. in Hotan Black Chickens in China reveals two novel subtypes of Cryptosporidium meleagridis

A total of 617 fecal specimens were collected on 18 Hotan Black chicken farms in Southern Xinjiang, China, and tested for the presence of Cryptosporidium spp. by PCR of the small subunit ribosomal RNA (SSU rRNA) gene. The overall infection rate by Cryptosporidium spp. was 11.5% (71/617), and ten of the 18 farms were positive. The infection rate by Cryptosporidium spp. was 14.5% (48/331) in the 30–60 d group, higher than chickens in the <30 d (12.0%, 15/125), 60–90 d (6.9%, 5/72), and >90 d (3.4%, 3/89) groups. Cryptosporidium meleagridis (n = 38) and C. baileyi (n = 33) were confirmed by sequencing analysis. A total of 25 of the 38 C. meleagridis-positive specimens were subtyped successfully at the gp60 gene, including one known subtype (IIIbA23G1R1, n = 1) and two novel subtypes, named IIIbA25G1R1 (n = 20) and IIIbA31G1R1 (n = 4). The results showed that infection by Cryptosporidium spp. in Hotan Black Chickens was common in this area and the distribution of C. meleagridis subtypes had regional characteristics.