BackgroundCryptosporidium spp., Giardia duodenalis and Enterocytozoon bieneusi are common enteric pathogens in humans and animals. Data on the transmission of these pathogens are scarce from Guangdong, China, which has a subtropical monsoon climate and is the epicenter for many emerging infectious diseases. This study was conducted to better understand the prevalence and identity of the three pathogens in pre-weaned dairy calves in Guangdong.MethodsThe occurrence and genetic identity of three pathogens were analyzed by polymerase chain reaction. PCR-positive products were sequenced to determine the species and genotypes. A Chi-square test was used to compare the prevalence of pathogens among sampling dates, age groups, or clinical signs.ResultsThe detection rates of Cryptosporidium spp., G. duodenalis and E. bieneusi were 24.0% (93/388), 74.2% (288/388) and 15.7% (61/388), respectively. Three Cryptosporidium species were detected, including C. bovis (n = 73), C. parvum (n = 12) and C. ryanae (n = 7); one animal had concurrence of C. bovis and C. parvum. C. parvum was the dominant species during the first two weeks of life, whereas C. bovis and C. ryanae were mostly seen at 3–9 weeks of age. Sequence analysis identified the C. parvum as subtype IIdA19G1. Assemblage E (n = 282), assemblage A (n = 1), and concurrence of A and E (n = 5) were identified among G. duodenalis-positive animals using multilocus genotyping (MLG). Altogether, 15, 10 and 17 subtypes of assemblage E were observed at the bg, gdh and tpi loci, respectively, forming 49 assemblage E MLGs. The highest detection rate of G. duodenalis was found in winter. Sequence analysis identified genotypes J (n = 57), D (n = 3) and one concurrence of J and D among E. bieneusi-positive animals. The detection rate of E. bieneusi was significantly higher in spring (38.0%; 41/108) than in summer (7.2%; 8/111) and winter (7.1%; 12/169).ConclusionsThese results indicate a common occurrence of C. parvum subtype IIdA19G1, G. duodenalis assemblage E, and E. bieneusi genotype J in pre-weaned dairy calves in Guangdong. More studies are needed to understand the unique genetic characteristics and zoonotic potential of the three enteric pathogens in the province.

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Background Enterocytozoon bieneusi and Giardia duodenalis are common human and animal pathogens. Studies have increasingly shown that non-human primates (NHPs) are common hosts of these two zoonotic parasites. However, few studies have explored the genetic diversity and public health potential of these pathogens in laboratory monkeys. In this study, we examined the genetic diversity of the two pathogens in crab-eating macaques ( Macaca fascicularis ) in a commercial facility in Hainan, China. Results Enterocytozoon bieneusi and G. duodenalis were detected by PCR analysis in 461/1452 (31.7%) and 469/1452 (32.3%) fecal specimens from the animals, respectively. Significantly higher detection rates of E. bieneusi were detected in males (36.5%, 258/706) than in females (26.7%, 160/599; χ 2 = 14.391, P = 0.0001), in animals with loose stools (41.4%, 151/365) than those with normal stool (28.5%, 310/1087; χ 2 = 20.83, P < 0.0001), and in animals of over 3 years of age (38.6%, 135/350) than those of 1–3 years (29.6%, 326/1,102; χ 2 = 9.90, P = 0.0016). For G. duodenalis , the detection rate in males (33.4%, 236/706) was higher than in females but not statistically significant (30.2%, 181/599; χ 2 = 1.54, P = 0.2152), in monkeys with loose stools (41.1%, 150/365) than those with normal stools (29.3%, 319/1087; χ 2 = 17.25, P < 0.0001), and in monkeys of 1–3 years of age (36.6%, 403/1102) than those over 3 years (18.9%, 66/350; χ 2 = 38.11, P < 0.0001). Nine E. bieneusi genotypes were detected in this study by DNA sequence analysis of the internal transcribed spacer of the rRNA gene, namely Type IV (236/461), Peru8 (42/461), Pongo2 (27/461), Peru11 (12/461), D (4/461) and PigEbITS7 (1/461) previously seen in NHPs as well as humans, and CM1 (119/461), CM2 (17/461) and CM3 (3/461) that had been only detected in NHPs. DNA sequence analyses of the tpi , gdh and bg loci identified all G. duodenalis specimens as having assemblage B. Altogether, eight (4 known and 4 new), seven (6 known and 1 new) and seven (4 known and 3 new) subtypes were seen at the tpi , gdh and bg loci, leading to the detection of 53 multi-locus genotypes (MLG-B-hn01 to MLG-B-hn53). Most of them were genetically related to those p...

The influence of fluoride on the anodic dissolution kinetics of titanium was studied by several electrochemical techniques at steady-state open-circuit potentials in 1.0 M HClO 4 containing fluoride with various concentrations ranging from 0 to 0.1 M. The promoting effect of fluoride ͑especially when ͓F − ͔ Ͼ 1 ϫ 10 −3 M͒ on the anodic dissolution behavior of titanium was characterized and discussed by taking into account the changes in the estimated electrochemical and kinetic parameters. The faradaic impedance for the anodic dissolution of titanium was analyzed both by fitting based on an equivalent electrical circuit model and by theoretical derivation based on a two-step mechanism involving one adsorbed intermediate species. By correlating the faradaic impedance expression derived from the dissolution mechanism with that deduced from the equivalent electrical circuit model, some important kinetic parameters ͑such as the apparent rate constants K 1 and K 2 and the surface coverage ss ͒ could be estimated from the equivalent circuit elemental parameters ͑such as R ct , R a , and C a ͒. The charge-transfer reaction was the rate-determining step at lower fluoride concentrations of ͓F − ͔ Յ 1 ϫ 10 −3 M, leading to a high surface coverage of ss Ϸ 1, while the chemical dissolution reaction is the rate-determining step at higher fluoride concentrations of ͓F − ͔ Ͼ 1 ϫ 10 −3 M, leading to a decreased surface coverage of ss Ͻ 0.5.Titanium ͑and its alloys͒ is one of the most important metal materials widely used in engineering and technological applications. 1 Titanium-based materials possess excellent corrosion resistance in various electrolyte solutions due to the easy formation of a highly protective oxide film at the titanium ͑and its alloys͒ surface. But some aggressive inorganic anions such as F − and Cl − existing in aqueous environments can attack the passivity of titanium and its alloys. [2][3][4] The effects of solution pH and fluoride concentration on the anticorrosion properties of the surface passive TiO 2 films formed by anodic oxidation of titanium at different passivation potentials were widely investigated by many researchers using various electrochemical and surface analytical techniques. 3,5-10 The active-passive transition kinetics of titanium in electrolyte solutions without 11-15 and with fluoride 9,16 was also studied using various electrochemical methods. However, very few studies were reported on the dissolution mechanism and kinetics of titanium in fluoride-containing solutions at open-circuit potentials ͑OCPs͒. 16 Recently, we investigated the influence of fluoride concentration and the film formation potential on the bulk and surface properties of anodic oxide films ͑as well as their breakdown͒ formed on titanium in fluoride-containing perchloric solutions. 3 The passivity of titanium would be destroyed by the chemical dissolution of the oxide if the fluoride concentration was higher than 1 ϫ 10 −3 M. 3 This work investigates the effect of fluoride on the anodic dissolution kinetics of metal ...