On the transmissibility of Eperythrozoon suis by Stomoxys calcitrans and Aedes aegypti

Hemotrophic Mycoplasmas-Vector Transmission in Livestock

Hemotrophic mycoplasmas (HMs) are highly host-adapted and specialized pathogens infecting a wide range of mammals including farm animals, i.e., pigs, cattle, sheep, and goats. Although HMs have been known for over 90 years, we still do not know much about the natural transmission routes within herds. Recently, it has been repeatedly discussed in publications that arthropod vectors may play a role in the transmission of HMs from animal to animal. This is mainly since several HM species could be detected in different potential arthropod vectors by PCR. This review summarizes the available literature about the transmission of bovine, porcine, ovine, and caprine HM species by different hematophagous arthropod vectors. Since most studies are only based on the detection of HMs in potential vectors, there are rare data about the actual vector competence of arthropods. Furthermore, there is a need for additional studies to investigate, whether there are biological vectors in which HMs can multiply and be delivered to new hosts.

Haemotrophic Mycoplasmas Infecting Pigs: A Review of the Current Knowledge

Haemotrophic mycoplasmas (haemoplasmas) are a group of highly specific and adapted bacteria. Three different haemoplasma species in pigs are known to date: Mycoplasma (M.) suis, M. parvum and 'Candidatus (Ca.) M. haemosuis'. Even though these bacteria have been known in pig farming for a long time, it is difficult to draw general conclusions about the relevance of their infections in pigs. This review summarizes the current knowledge on the three porcine haemoplasma species with regards to clinical and pathological descriptions, pathobiology, epidemiology and diagnostics as well as prevention and therapy. Overall, it is clear that considerably more data are available for M. suis than for the other two species, but generally, porcine haemoplasmas were found to be highly prevalent all over the world. Mycoplasma suis is the most virulent species, causing acute infectious anaemia in pigs (IAP), whereas M. parvum usually results in chronic and subclinical infections associated with performance losses. Little is known about the clinical significance of the recently discovered third porcine species 'Ca. M. haemosuis'. So far, the described pathogenic mechanisms mainly include direct destruction of erythrocytes via adhesion, invasion, eryptosis and nutrient scavenging, indirect erythrocyte lysis due to immune-mediated events and immune dysregulation processes. A review of published diagnostic data confirms PCR assays as the current standard method, with various cross-species and species-specific protocols. Overall, there is a need for further examination to obtain valuable insights for practical application, specifically regarding the importance of subclinical infections in naturally infected animals. An essential requirement for this will be to gain a more comprehensive understanding of the mechanisms operating between the host and the pathogen.

Bleeding skin lesions in gestating sows of a piglet producing farm in Austria

BACKGROUND

Stomoxys calcitrans, the stable fly, occurs in pig producing countries worldwide. While in cattle the impact of this blood sucking insect is quite well described, its role in pig production is poorly investigated. Here we describe a case of a massive stable fly overpopulation in the gestation unit of a piglet producing farm in Austria that resulted in bleeding skin lesions in bitten sows.

CASE PRESENTATION

In October 2021, the responsible herd veterinarian of the case farm reported of sows in the gestation area presenting with bloody crusts on the whole skin surface of the body and of bleeding skin lesions. 33/55 sows were affected by moderate to severe skin lesions. Reproductive performance decreased during the time of massive stable fly overpopulation. Sows in the gestation unit showed defensive behaviour and at a certain time point resigned and accepted being bitten by stable flies. After controlling the fly population, reproductive performance improved and even exceeded the performance before the massive overgrowth of the stable fly population.

CONCLUSIONS

Stable flies are a serious harm to pigs and should be kept in mind for improved animal health and welfare. Knowledge about the determination of Stomoxys calcitrans and early recognition of an increasing stable fly population in pig farming systems followed by proper insect control measures have to be performed to reduce losses caused by this harming insect.

Establishment of molecular diagnostics targeting the 23S ribosomal RNA gene for the detection of Mycoplasma suis infection in Thai domestic pigs

Mycoplasma (M.) suis is a pathogenic hemotropic Mycoplasma sp. that causes acute hemolytic anemia or chronic infection in pigs. M. suis infection can be diagnosed using several methods, including molecular diagnosis such as conventional PCR (cPCR) and quantitative PCR (qPCR). In these cases, the common target is the 16S rRNA gene; however, this genetic marker cannot distinguish hemoplasma at the species level owing to high sequence identity. Therefore, the 23S rRNA gene has emerged as another target gene. Other than PCR, the loop-mediated isothermal amplification (LAMP) method can be applied for M. suis. The objective of the present study was to establish cPCR, TaqMan qPCR, and LAMP assays in which the 23S rRNA gene is used to detect M. suis infection in Thai domestic pigs. The analytical sensitivity of cPCR was determined as 7.46 × 10⁴ copies/μl of plasmid DNA, whereas those of qPCR and LAMP were 7.46 × 10² copies/μl. There was no cross reaction with other pathogens in any of the assays. To evaluate the diagnostic performance of the assays, they were tested using 173 samples of genomic DNA. The detection percentage of M. suis infection was 24.86% (43/173; 95% CI: 18.61%-31.89%), 28.32% (49/173; 95% CI: 21.75%-35.66%), and 29.48% (51/173; 95% CI: 22.80%-36.88%) using cPCR, qPCR, and LAMP, respectively. Using qPCR as a reference assay, cPCR showed 81.63% sensitivity, 97.58% specificity, and an almost perfect level of agreement (kappa = 0.823). In comparison, LAMP showed 77.55% sensitivity, 89.52% specificity, and a substantial level of agreement (kappa = 0.662). All assays tested here could be applied in veterinary diagnostic laboratories for monitoring porcine health in the herds. Furthermore, the LAMP assay could be used as a screening test in farm practice without the need for any special equipment.

Potential mosquito vector attraction to- and feeding preferences for pigs in Romanian backyard farms

Introduction

Mosquitoes either biologically or mechanically transmit various vector-borne pathogens affecting pigs. Mosquito species display a wide variety of host preference, as well as host attraction and behaviours. Mosquito species attraction rates to- and feeding rates on pigs or other potential hosts, as well as the seasonal abundance of the mosquito species affects their pathogen transmission potential.

Methods

We caught mosquitoes in experimental cages containing pigs situated in Romanian backyard farms. The host species of blood meals were identified with PCR and sequencing.

Results

High feeding preferences for pigs were observed in Aedes vexans (90%), Anopheles maculipennis (80%) and Culiseta annulata (72.7%). However, due to a high abundance in the traps, Culex pipiens/torrentium were responsible for 37.9% of all mosquito bites on pigs in the Romanian backyards, despite low feeding rates on pigs in the cages (18.6%). We also found that other predominantly ornithophilic mosquito species, as well as mosquitoes that are already carrying a blood meal from a different (mammalian) host, were attracted to backyard pigs or their enclosure.

Discussion

These results indicate that viraemic blood carrying, for instance, African swine fever virus, West-Nile virus or Japanese encephalitis virus could be introduced to these backyard pig farms and therefore cause an infection, either through subsequent feeding, via ingestion by the pig or by environmental contamination.

Molecular detection of Mycoplasma wenyonii and its closely related hemotropic Mycoplasma sp. in blood-sucking flies from a buffalo farm in Chachoengsao province, Thailand

Bovine hemoplasmosis is a disease in buffaloes and cattle caused by hemotropic mycoplasmas or hemoplasmas. Only two bovine hemoplasma species, Mycoplasma wenyonii and Candidatus Mycoplasma haemobos, have been described in several countries. Hemoplasmas induce acute hemolytic anemia or chronic infection, leading to production loss. Bovine hemoplasma DNA was also detected in blood-sucking arthropods, suggesting vector transmission in farms. To date, no studies of the molecular detection of bovine hemoplasmas in Thai buffaloes and arthropod vectors have been reported. This study aimed to study the 1-year diversity of hematophagous flies in a buffalo farm located in Chachoengsao province, Thailand, and to investigate the molecular occurrence of bovine hemoplasmas in those flies using a polymerase chain reaction (PCR) assay and sequence analyses. A total of 1,488 mosquitoes, 867 stable flies, and 312 tabanid flies were collected during this study. The most abundant mosquitoes, stable flies, and tabanid flies were Culex tritaeniorhynchus, Stomoxys calcitrans, and Tabanus megalops, respectively. A total of 249 genomic DNA samples of flies were tested using a PCR assay based on the 16S rRNA gene; 23.69% (59/249) of the insect samples were positive in this assay. Positive samples (n = 8) were subjected to bidirectional sequencing. The BLAST results showed that only three samples from Stomoxys calcitrans and two samples from Tabanus megalops showed 99.90% and 99.17% similarities to the M. wenyonii isolate B003 (MG948626/Water buffalo/Cuba) and the M. wenyonii isolate C124 (MG948625/Cattle/Cuba), respectively. This molecular occurrence of bovine hemoplasmas in blood-sucking flies suggested that those flies are the mechanical vectors for bovine hemoplasmas in Thailand. Based on the phylogenetic analysis of the 16S rRNA gene, the sequences of M. wenyonii were likely classified into two subgroups (A and B), suggesting closely related bovine hemoplasma species. Finally, the genetic analysis of the 23S rRNA gene from these two subgroups revealed that subgroup A could be M. wenynoii and subgroup B may be a subspecies of M. wenyonii or another putative novel species. However, further investigation should be conducted in buffaloes, cattle, and blood-sucking flies to gain more 16S rRNA and 23 rRNA gene sequences of bovine hemoplasmas.

Update on shedding and transmission routes of porcine haemotrophic mycoplasmas in naturally and experimentally infected pigs

Horizontal transmission of Mycoplasma suis via parenteral exposure during standard practices or through bites during fightings have been identified as key epidemiological routes. However, as knowledge gaps on other potential shedding and transmission routes exist, the present study combines both laboratory experiments and field surveys to gain new insights into the epidemiology of porcine haemotrophic mycoplasmas. Splenectomised pigs were orally inoculated with a M. suis field strain and investigated for clinical signs related to infectious anaemia of pigs (IAP) and the presence of M. suis in blood, urine and saliva samples by qPCR. All blood samples were negative for M. suis and animals did not show obvious clinical signs of IAP throughout the entire study period. Additionally, urine, nasal and saliva samples from sows of conventional piglet producing farms and semen samples from a boar stud revealed no detection of M. suis and ‘Candidatus Mycoplasma haemosuis’ by qPCR. Thus, the results indicate that blood-independent transmission routes might be of minor relevance under field conditions.

Mo­lecular evidence and epidemiology of “Candidatus Mycoplasma haemobos” among cattle in Peninsular Malaysia using the 16S rRNA gene

Haemotropic Mycoplasma infection among cattle has not been seriously looked into, despite the fact it is associated with poor weight gain and depression. One thousand and forty-five blood samples from apparently healthy cattle from forty-three farms within the entire Peninsular Malaysia were exa­mined over a one-year period. Using polymerase chain reaction to amplify the 16S rRNA gene, the presence of “Candidatus Mycoplasma haemobos” as one of the haemotropic Mycoplasma species that affects cattle in the country was detected. Forty-seven percent of the sampled population was positive for “C. M. haemobos”, with the antigen present in all herds sampled. Breed of cattle, gender, age, production type, physiological status, herd size, management system, farm size, farm age, prophylactic treatment against blood parasites, presence of ticks, frequency of de-ticking, zone, closeness to forest, closeness to waste area, closeness to human settlement and closeness to body of water were all significantly associated (P<0.05) with the detection of “C. M. haemobos”. The findings from this study will be pivotal in government policy on this blood Mycoplasma infection, as the study happens to be the first comprehensive molecular survey of the microorganism in the country.

The Stable Fly (Stomoxys calcitrans) as a Possible Vector Transmitting Pathogens in Austrian Pig Farms

This pilot study aimed to investigate stable flies from Austrian pig farms for the presence of defined swine pathogens, such as porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus 2 (PCV2), hemotrophic mycoplasmas in ingested blood and/or body parts and bacteria on the surface of the flies. Furthermore, the use of stable flies as a diagnostic matrix for the detection of pathogens in the ingested pig blood should be investigated. In total, 69 different microorganisms could be found on the surface of tested S. calcitrans from 20 different pig farms. Escherichia coli was the most common bacterium and could be found on flies from seven farms. In seven farms, hemotrophic mycoplasmas were detected in stable flies. PRRSV could not be found in any of the samples of these 20 farms but PCV2 was detected in six farms. Whether the stable fly can be used as a matrix to monitor the health status cannot be accurately determined through this study, especially in regard to PRRSV. Nevertheless, it might be possible to use the stable fly as diagnostic material for defined pathogens like Mycoplasma suis and PCV2.

Prevalence and phylogenetic analysis of hemoplasma species in domestic pigs in Korea

Background

Two hemoplasma species, Mycoplasma suis and M. parvum, previously known as Eperythrozoon suis and E. parvum, respectively, have been identified in pigs. Swine hemoplasmosis is a global problem, and M. suis infection results in economic losses to pig producers worldwide. This study investigated the frequency and distribution of hemotropic mycoplasmas in pig farms of Korea. As hemoplasmas can be transmitted by ticks, we also analyzed the presence of the tick-borne pathogens Anaplasma spp. and Borrelia spp.

Methods

We screened 1867 samples from 464 pig farms located in four regions of Korea over the period from 2014 to 2018. PCR-positive samples were further analyzed by nucleotide sequencing and phylogenetic analysis of pathogen-specific markers for species identification.

Results

Of the 1867 pigs evaluated in the study, three (0.2%), 51 (2.7%), and one (0.1%) were found to be infected with M. suis, M. parvum, and the novel hemotropic M. haemosuis, respectively; Anaplasma spp. and Borrelia spp. were not detected. The 16S rRNA sequences of M. suis, M. parvum, and the novel hemotropic M. haemosuis were highly similar (99.3–100%, 99.6–100%, and 99.6–100%, respectively) to those of Mycoplasma spp. isolated from other countries. To the best of our knowledge, this is the first nationwide, large-scale study of the molecular detection of Mycoplasma spp. in domestic pigs in Korea.

Conclusions

Our results indicate that Mycoplasma infections are widespread in Korean domestic pigs, and that continuous monitoring and control strategies are required to prevent the spread of hemoplasmas, which, in addition to causing economic losses in the pig industry, pose a potential threat to public health. As transmission routes of hemoplasmas remain unelucidated, additional epidemiological studies are recommended to identify reservoirs and vectors of Mycoplasma spp. in Korea.

Detection of Mycoplasma suis in pre-suckling piglets indicates a vertical transmission

Background

Transmission of Mycoplasma (M.) suis mainly occurs via iatrogenic or zootechnical manipulations or due to ranking fights. Other transmission routes including ingestion of secretes/excretes; blood-sucking arthropods and intra-uterine transmission have thought to play an epidemiological role without being experimentally proven. To investigate a vertical transmission of M. suis under field conditions blood samples from pre-suckling piglets and their corresponding dam were examined for M. suis by quantitative polymerase chain reaction (qPCR) in 21 farms in Southern Germany.

Results

A total of 14.35% of the 474 blood samples from pre-suckling piglets reacted qPCR positive. Additionally, M. suis was detected in 65 (31.25%) of the 208 sows at farrowing. On farm level, 16 (76.2%) of the 21 farms had at least one M. suis positive animal. M. suis positive farms had an average of 0.41 more stillborn piglets per litter than M. suis negative farms (p = 0.007).

Conclusion

The present study provides further insights into M. suis infection dynamics as it is the first detection of M. suis in piglets immediately after birth prior to colostrum intake and the first large scale investigation of M. suis in sows at farrowing.

Molecular detection of Bartonella species and haemoplasmas in wild African buffalo (Syncerus caffer) in Mozambique, Africa

The African buffalo (Syncerus caffer), a mammal species whose population is declining, can play a role as a reservoir or carrier of a wide number of arthropod-borne pathogens. Translocation procedures have been used as an alternative approach for species conservation. However, the veterinary aspects of this sort of procedures are extremely important to minimize the impact on animal health. In order to detectBartonellaand haemoplasmas, two important group of bacterial that have an impact in both human and animal health, EDTA whole-blood samples were screened for the presence of these bacterial pathogens by molecular techniques. As a result, a molecular occurrence of 4.1 and 15.4% forBartonellaspp. and haemoplasmas, respectively, was reported among 97 wild buffaloes sampled during a translocation procedure from Marromeu to Gorongosa Reserve, Mozambique. Additionally, phylogenetic analyses of the obtained sequences were conducted. At least, three bovine-associated pathogens, namelyB. bovis,M. wenyoniiand ‘CandidatusM. haemobos’, as well as a probably newBartonellagenotype/species were detected inS. caffer.Further studies are needed in order to determine whether these bacterial species may cause impact in buffaloes and other sympatric ruminant species living in the release site.

Tick- and fly-borne bacteria in ungulates: the prevalence of Anaplasma phagocytophilum, haemoplasmas and rickettsiae in water buffalo and deer species in Central Europe, Hungary

Background

Hunting constitutes an important industry in Europe. However, data on the prevalence of vector-borne bacteria in large game animal species are lacking from several countries. Blood or spleen samples (239 and 270, respectively) were taken from red, fallow and roe deer, as well as from water buffaloes, mouflons and wild boars in Hungary, followed by DNA extraction and molecular analyses for Anaplasma phagocytophilum, haemoplasmas and rickettsiae.

Results

Based on blood samples, the prevalence rate of A. phagocytophilum infection was significantly higher in red deer (97.9%) than in fallow deer (72.7%) and roe deer (60%), and in all these compared to mouflons (6.3%). In addition, 39.2% of the spleen samples from wild boars were PCR positive for A. phagocytophilum, but none of the buffalos. Based on blood samples, the prevalence rates of both Mycoplasma wenyonii (Mw) and ‘Candidatus M. haemobos’ (CMh) infections were significantly higher in buffaloes (Mw: 91.2%; CMh: 73.3%) than in red deer (Mw: 64.6%; CMh: 45.8%), and in both of them compared to fallow deer (Mw: 30.3%; CMh: 9.1%) and roe deer (Mw: 20%; CMh: 1.5%). The prevalence of Mw and CMh infection significantly correlated with the body sizes of these hosts. Furthermore, Mw was significantly more prevalent than CMh in buffaloes, red and roe deer. Mycoplasma ovis was detected in mouflons, M. suis in wild boars, R. helvetica in one fallow deer and one mouflon, and an unidentified Rickettsia sp. in a fallow deer.

Conclusions

Forest-dwelling game animal species were found to be important carriers of A. phagocytophilum. In contrast, animals grazing grassland (i.e. buffaloes) were less likely to get infected with this Ixodes ricinus-borne pathogen. Water buffaloes, deer species, mouflons and wild boars harbored haemoplasmas that may affect domestic ungulates. Evaluated animals with larger body size had significantly higher prevalence of infection with haemoplasmas compared to smaller deer species. The above host species rarely carried rickettsiae.

High occurrence of Mycoplasma suis infection in swine herds from non-technified farms in Mossoró, state of Rio Grande do Norte, Northeastern Brazil

Mycoplasma suis, the etiological agent of swine hemoplasmosis, has been neglected in swine herds around the world. Swine hemoplasmosis is frequently associated with hemolytic anemia, disgalacty, infertility and immunosuppression, and it results in significant economic losses. This study investigates the occurrence of M. suis in non-technified swine herds in the northeastern region of Brazil using quantitative PCR (qPCR) based on the 16S rRNA gene. Between March and August 2013, blood samples from 147 swine were collected during slaughter in the city of Mossoró, state of Rio Grande do Norte, northeastern Brazil. One hundred and twelve samples (76.19%) were positive for M. suis by qPCR assays. The range of Cqs and quantification (copies of a M. suis-16S rRNA gene fragment/µL) was 20.86-37.89 and 1.64×101-6.64×107, respectively. One can conclude that M. suis infection have high occurrence (76,19%) in non-technified swine-rearing systems in Mossoró in the state of Rio Grande do Norte, Brazil.

Occurrence of Mycoplasma haemocanis in dogs infested by ticks in Campo Grande, Mato Grosso do Sul, Brazil

Abstract Hemotropic mycoplasmas in dogs, such as Mycoplasma haemocanis, have been described worldwide. Recently, these pathogens have been reported to be causative agent of zoonosis. It is known that its transmission may occur through the action of blood-sucking arthropods (e.g. ticks or fleas), through blood transfusion, contaminated fomites and/or transplacentally. In Brazil, M. haemocanis is present in practically all regions and the tick Rhipicephalus sanguineus sensu lato is suspected the main vector. In the municipality of Campo Grande, state of Mato Grosso do Sul, there is little information about infection of dogs by M. haemocanis, or on the main epidemiological features associated with it. Thus, the aim of the present study was to determine the occurrence of M. haemocanis among dogs infested by ticks and to assess possible associations with some epidemiological factors. The polymerase chain reaction (PCR) and DNA sequencing were used to analyze dog blood samples (n = 94). DNA from M. haemocanis was detected in four samples. No significant associations were observed with any epidemiological parameter analyzed here. However, the results from this study confirm that this pathogen is circulating in this region and should be considered in the differential diagnosis of diseases among anemic dogs.

Seroprevalence and risk factors of Mycoplasma suis infection in pig farms in central China

Mycoplasma suis, the causative agent of porcine infectious anemia, causes large economic losses to the swine industry worldwide. A questionnaire-based survey was conducted in 69 pig farms in Hubei Province, China, from November 2011 to August 2013 to ascertain the prevalence and associated risk factors of M. suis. Four thousand and four blood samples from pigs of all the age groups were tested for M. suis antibodies using the established rMSG1-ELISA assay. Among these 4004 samples, 1615 blood samples from multiparous sows were examined to identify the association between seroprevalence and different seasons. Information on risk factors collected from farmers or attending veterinarians was recorded on a pre-designed questionnaire. The overall test seroprevalence of M. suis infection at the animal level was 31.9% (1277/4004; 95% CI: 30.5%, 33.4%), whereas at the farm level, this value was 95.65% (66/69; 95% CI: 87.8%, 99.1%). The seroprevalence of M. suis was higher in replacement gilts (40.6%; 95% CI: 35.1%, 46.3%), multiparous sows (48.2%; 95% CI: 45.8%, 50.7%) and boars (44.4%; 95% CI: 34.5%, 54.8%), as compared to piglets (13.0%; 95% CI: 9.4%, 17.3%), weaned-piglets (10.8%; 95% CI: 8.9%, 13.0%), and growing-finishing pigs (25.0%; 95% CI: 22.0%, 28.3%). In terms of seasons, the prevalence of M. suis in pigs was significantly higher in summer (65.3%; 95% CI: 61.0%, 69.5%) and autumn (65.0%; 95% CI: 59.0%, 70.6%) compared to spring (30.1%; 95% CI: 26.0%, 34.4%) and winter (36.4%; 95% CI: 31.4%, 41.5%). Farm-level risk factors were identified by multivariable logistic regression analysis. The associated factors retained in the final multivariable logistic regression model were drug treatment, presence of mosquitoes and flies, and frequency of disinfection. Drug treatment (OR=0.24; 95% CI: 0.07, 0.88; P=0.031) and frequency of disinfection (OR=0.23; 95% CI: 0.06, 0.90; P=0.035) were protective factors, and the presence of mosquitoes and flies (OR=5.994; 95% CI: 1.56, 23.00; P=0.009) was a risk factor for M. suis infection on farms. The results of the present study provide the first insight into the impact of associated determinants on M. suis infection in central China.

Quantitative PCR analysis of Mycoplasma suis shedding patterns during experimental infection

The uncultivable hemotrophic bacterium Mycoplasma suis causes infectious anemia in pigs worldwide. The mechanisms by which M. suis is transmitted from pig to pig are largely unknown. Thus, the present study aimed at investigating urine, feces, saliva, nasal and vaginal secrets as well as environmental samples for the presence of M. suis DNA to get insights into potential transmission routes. Seven pigs were experimentally infected with M. suis KI3806. Samples were taken for 8 days post infection (p.i.). A quantitative LightCycler msg1 PCR was used to detect and quantify M. suis. Shedding was found in saliva as well as nasal and vaginal secrets from day 6 p.i. on with a quantity of 3.4 × 10(2) to 2.7 × 10(5)M. suis/swab. In urine M. suis DNA could be detected in 100.0% of the samples from day 6 p.i. on with a quantity of 4.7 × 10(2) to 6.3 × 10(5)M. suis per mL. When shedding patterns were correlated to the median bacterial blood loads shedding was observed at loads of 2.0 × 10(9)-7.0 × 10(10)M. suis per mL blood. No M. suis DNA could be amplified from feces. Dust and water samples of the pig drinking troughs were positive for M. suis on days 2 and 6 post infection, air samples were M. suis-negative throughout the experiment. Our results indicate that blood independent direct transmission as well as indirect transmission via environmental contamination could play a role in the epidemiology of M. suis infections.

Mathematical modelling and evaluation of the different routes of transmission of lumpy skin disease virus

Lumpy skin disease (LSD) is a severe viral disease of cattle. Circumstantial evidence suggests that the virus is transmitted mechanically by blood-feeding arthropods. We compared the importance of transmission via direct and indirect contact in field conditions by using mathematical tools. We analyzed a dataset collected during the LSD outbreak in 2006 in a large dairy herd, which included ten separated cattle groups. Outbreak dynamics and risk factors for LSD were assessed by a transmission model. Transmission by three contact modes was modelled; indirect contact between the groups within a herd, direct contact or contact via common drinking water within the groups and transmission by contact during milking procedure. Indirect transmission was the only parameter that could solely explain the entire outbreak dynamics and was estimated to have an overall effect that was over 5 times larger than all other possible routes of transmission, combined. The R0 value induced by indirect transmission per the presence of an infectious cow for 1 day in the herd was 15.7, while the R0 induced by direct transmission was 0.36. Sensitivity analysis showed that this result is robust to a wide range of assumptions regarding mean and standard deviation of incubation period and regarding the existence of sub-clinically infected cattle. These results indicate that LSD virus spread within the affected herd could hardly be attributed to direct contact between cattle or contact through the milking procedure. It is therefore concluded that transmission mostly occurs by indirect contact, probably by flying, blood-sucking insects. This has important implications for control of LSD.

A quantitative TaqMan PCR assay for the detection of Mycoplasma suis

AIM

To develop a TaqMan probe-based, highly sensitive and specific quantitative PCR (qPCR) assay for the detection and quantification of Mycoplasma suis in the blood of pigs.

METHODS AND RESULTS

Primers and probes specific to Myc. suis 16S rRNA gene were designed. The qPCR assay's specificity, detection limit, intra- and inter-assay variability were evaluated and its performance was compared with a Myc. suis conventional PCR assay (cPCR). Blood of two experimentally infected pigs, 40 Indiana pigs, 40 Brazilian sows and 28 peccaries were tested. The assay detected as few as ten copies of Myc. suis plasmids and was 100-fold more sensitive than the cPCR. No cross-reactivity with nontarget pig mycoplasmas was observed. An average of 1·62 × 10(11) and 2·75 × 10(8) target copies ml(-1) of blood were detected in the acutely and chronically infected pigs, respectively. Three (7·5%) pigs and 32 (80·0%) sows were positive while all peccaries were negative for Myc. suis.

CONCLUSION

The developed qPCR assay is highly sensitive and specific for Myc. suis detection and quantification.

SIGNIFICANCE AND IMPACT OF THE STUDY

TaqMan qPCR is an accurate and quick test for detection of Myc. suis infected pigs, which can be used on varied instrumentation platforms.

Molecular investigation of transplacental and vector-borne transmission of bovine haemoplasmas

The present study was carried out in a herd with concurrent infections of Mycoplasma wenyonii and 'Candidatus M. haemobos', to investigate if transplacental and/or vector-borne transmission is possible for one or both bovine haemoplasma species. For this purpose blood samples were collected from 38 mother animals and their newborn calves; as well as from 17 uninseminated cows twice three months apart. In addition, 311 mosquitoes and blood-sucking flies (Diptera: Culicidae, Tabanidae, Muscidae) were cought near the animals. DNA was extracted from all samples, followed by real-time PCR analysis. In 10.5% of neonate calves, that were born to cows harbouring both haemoplasmas, M. wenyonii and/or 'Candidatus M. haemobos' positivity was detected. Copy numbers in positive samples from cows and their calves indicated that - in comparison with M. wenyonii - 'Candidatus M. haemobos'-bacteraemia had usually lower levels. In samples of uninseminated cows the rate of infection with the latter species decreased. These findings may explain why M. wenyonii was significantly more frequently detected in blood-sucking flies, than 'Candidatus M. haemobos'. In conclusion, molecular evidence is provided for the first time on the transplacental transmission of bovine haemoplasmas. Regarding their spread by blood-sucking arthropods, new potential vectors were identified, i.e. the horn fly (Haematobia irritans), the stable fly (Stomoxys calcitrans) and two species of horse flies (Tabanus bovinus, T. bromius).

Identification, molecular characterization, and occurrence of two bovine hemoplasma species in Swiss cattle and development of real-time TaqMan quantitative PCR assays for diagnosis of bovine hemoplasma infections

Concomitantly with an outbreak of fatal anaplasmosis in a cattle herd in Switzerland in 2002, we detected two bovine hemoplasma species in diseased animals: Mycoplasma wenyonii (formerly Eperythrozoon wenyonii) and a second, novel bovine hemoplasma species later designated "Candidatus Mycoplasma haemobos" (synonym, "Candidatus Mycoplasma haemobovis"). The second species was characterized by a shorter 16S rRNA gene. The aims of the present study were to provide a detailed molecular characterization of this species, to develop specific quantitative real-time PCR assays for the two bovine hemoplasma species, and to apply these assays in order to evaluate the prevalence and clinical significance of the hemoplasmas. Sequencing of the near-complete 16S rRNA gene of the second hemoplasma revealed that it was 94% identical to that of Mycoplasma haemofelis, an anemia-inducing feline hemoplasma species, but less than 85% identical to that of the bovine hemoplasma M. wenyonii. Using the newly developed assays, a total of 159 animals from the anaplasmosis outbreak were reexamined. In addition, we tested 57 clinically ill and 61 healthy Swiss cattle, as well as 47 calves. Both hemoplasmas were highly prevalent in adult cattle but occurred rarely in calves. Animals from the herd with the fatal anemia outbreak were more frequently infected with M. wenyonii and exhibited higher M. wenyonii blood loads than animals with unrelated diseases and healthy animals. Coinfections may increase the pathogenicity and clinical significance of bovine hemoplasmosis.

Prevalence of Mycoplasma suis (Eperythrozoon suis) infection in swine and swine-farm workers in Shanghai, China

OBJECTIVE

To determine the prevalence of Mycoplasma suis infection in swine, swine-farm workers, and swine veterinarians in Shanghai, China.

SAMPLE POPULATION

172 swine and 65 workers and veterinarians from 19 commercial swine farms.

PROCEDURES

Blood samples were collected from all study subjects. Blood samples were examined for the presence of M suis by means of compound and scanning electron microscopy. A species-specific PCR assay was developed for detection of M suis DNA extracted from blood samples. Relationships between infection status of swine and sex, age, geographic location, and clinical signs of disease were evaluated by use of a C(2) test. The phylogenetic relationship between partial 16S ribosomal RNA (rRNA) sequences from swine and human isolates of M suis was determined.

RESULTS

86% (148/172) of swine and 49% (32/65) of humans had positive PCR assay results for M suis infection. Swine infection status was not associated with any variable, with the exception of pyrexia and subcutaneous bleeding. The partial 16S rRNA sequences from human and swine isolates of M suis were 98% homologous and in the same phylogenetic cluster as a previously identified swine isolate of M suis.

CONCLUSIONS AND CLINICAL RELEVANCE

A large proportion of swine and humans in close contact with those swine were infected with M suis in Shanghai, China. The close phylogenetic relationship between swine and human isolates of M suis suggested possible interspecies transmission; however, additional research is required to better assess that possibility.

Transstadial and horizontal transfer of bacteria within a colony of Anopheles gambiae (Diptera: Culicidae) and oviposition response to bacteria-containing water

In a paratransgenic approach, genetically modified bacteria are utilized to kill the parasite in the vector gut. A critical component for paratransgenics against malaria is how transgenic bacteria can be introduced and then kept in a mosquito population. Here, we investigated transstadial and horizontal transfer of bacteria within an Anopheles gambiae mosquito colony with the focus on spiked breeding sites as a possible means of introducing bacteria to mosquitoes. A Pantoea stewartii strain, previously isolated from An. gambiae, marked with a green fluorescent protein (GFP), was introduced to mosquitoes in different life stages. The following life stages or older mosquitoes in the case of adults were screened for bacteria in their guts. In addition to P. stewartii other bacteria were isolated from the guts: these were identified by 16S rRNA sequence analysis and temporal temperature gradient gel electrophoresis (TTGE). Bacteria were transferred from larvae to pupae but not from pupae to adults. The mosquitoes were able to take up bacteria from the water they emerged from and transfer the same bacteria to the water they laid eggs in. Elizabethkingia meningoseptica was more often isolated from adult mosquitoes than P. stewartii. A bioassay was used to examine An. gambiae oviposition responses towards bacteria-containing solutions. The volatiles emitted from the solutions were sampled by headspace-solid phase microextraction (SPME) and identified by gas chromatography and mass spectrometry (GC-MS) analysis. P. stewartii but not E. meningoseptica mediated a positive oviposition response. The volatiles emitted by P. stewartii include indole and 3-methyl-1-butanol, which previously have been shown to affect An. gambiae mosquito behaviour. E. meningoseptica emitted indole but not 3-methyl-1-butanol, when suspended in saline. Taken together, this indicates that it may be possible to create attractive breeding sites for distribution of genetically modified bacteria in the field in a paratransgenic approach against malaria. Further research is needed to determine if the bacteria are also transferred in the same way in nature.

Alteration of integrin-associated protein (CD47) on experimental porcine eperythrozoonosis

To evaluate the alteration of CD47 on RBCs of pigs infected with M. suis, we induced the experimental porcine eperythrozoonosis and collected the blood samples at the different time points. The result of analysis by flow cytometry after reaction with mouse-anti-human CD47 and caprine-anti-mouse IgG-FITC reagents indicated that the CD47 quantity on RBCs changed correlatively with the course of PE. The lowest value of M1 (percentage of the positive cells in fluorescence intensity) occurred on day 7 post inoculation at the peak of parasitemia and decreased 82% compared with the control sample. And then, the values of M1 on day 14 and 21 rised slowly but were still significantly different with the controls (p < 0.01). These suggested that the quantity of CD47 on RBCs altered progressively with the phases of the PE disease. The decrease of CD47 on RBCs maybe weaken the inhibitory CD47-SIRPalpha interaction and provide positive signals for phagocytosis of macrophages resulting in the removal of the RBCs from the circulation. In conclusion, CD47, a marker on RBCs, maybe play an important role on the mechanism of hemolysis caused by infection of M. suis.

First LightCycler real-time PCR assay for the quantitative detection of Mycoplasma suis in clinical samples

Mycoplasma suis cannot be cultivated in vitro. Therefore, PCR-based methods are irreplaceable for the diagnosis of M. suis infections especially when clinical symptoms are not evident. Currently, no easy and reliable method allowing the quantitative detection of M. suis is available. This report describes the development of a quantitative LightCycler PCR assay based on the msg1 gene of M. suis (LC MSG1 PCR). No PCR signals were obtained with closely related haemotrophic and non-haemotrophic mycoplasmas, with other bacteria, and with M. suis-free blood and tissue arguing for a high analytical specificity. Test sensitivity was found to be 100%, and test specificity 96.7%. To test the diagnostic suitability of the LC MSG1 PCR, 25 pigs with clinical porcine eperythrozoonosis and 25 healthy pigs were investigated. All ill pigs revealed a positive real-time PCR result whereas only one healthy pig was detected to be M. suis-infected. M. suis was quantitatively detected in 19 blood specimens of 100 sows from Switzerland and in 17 of 160 post-weaning piglets from Germany. In conclusion, this new LC MSG1 PCR assay represents a powerful tool for the improvement of the current M. suis diagnosis and for prevalence and pathogenesis studies.

Investigating the endemic transmission of the hepatitis C virus

The hepatitis C virus (HCV) infects at least 3% of people worldwide and is a leading global cause of liver disease. Although HCV spread epidemically during the 20th century, particularly by blood transfusion, it has clearly been present in human populations for several centuries. Here we attempt to redress the paucity of investigation into how long-term endemic transmission of HCV has been maintained. Such transmission not only represents the 'natural' route of infection but also contributes to new infections today. As a first step, we investigate the hypothesis that HCV can be mechanically transmitted by biting arthropods. Firstly, we use a combined bioinformatic and geographic approach to build a spatial database of endemic HCV infection and demonstrate that this can be used to geographically compare endemic HCV with the range distributions of potential vector species. Second, we use models from mathematical epidemiology to investigate if the parameters that describe the biting behaviour of vectors are consistent with a proposed basic reproduction number (R0) for HCV, and with the sustained transmission of the virus by mechanical transmission. Our analyses indicate that the mechanical transmission of HCV is plausible and that much further research into endemic HCV is needed.

The detection of Mycoplasma (formerly Eperythrozoon) wenyonii by 16S rDNA PCR and denaturing gradient gel electrophoresis

Although the role of Mycoplasma wenyonii in disease is still subject to some debate, infections have been reported to result in parasitaemia, anaemia, scrotal and hind limb oedema, tachycardia, pyrexia, infertility, swollen teats, prefemoral lymphadenopathy and decreased milk production. Previously, diagnosis of M. wenyonii has been based on blood smears but is not specific for M. wenyonii and can be difficult to interpret. We have previously described the use of PCR and denaturing gradient gel electrophoresis (DGGE) for the detection and differentiation of Mycoplasma species. DGGE enables the rapid and specific identification of Mycoplasma species and is ideally suited to detecting both mixed infections and new and unusual species. In this study, we have used DGGE with universal primers to detect M. wenyonii DNA from blood samples. DGGE can be used on blood samples as a rapid and specific test for M. wenyonii and can also be used as a screening test for other blood borne pathogens.

16S rRNA gene-based identification of midgut bacteria from field-caught Anopheles gambiae sensu lato and A. funestus mosquitoes reveals new species related to known insect symbionts

Field-collected mosquitoes of the two main malaria vectors in Africa, Anopheles gambiae sensu lato and Anopheles funestus, were screened for their midgut bacterial contents. The midgut from each blood-fed mosquito was screened with two different detection pathways, one culture independent and one culture dependent. Bacterial species determination was achieved by sequence analysis of 16S rRNA genes. Altogether, 16 species from 14 genera were identified, 8 by each method. Interestingly, several of the bacteria identified are related to bacteria known to be symbionts in other insects. One isolate, Nocardia corynebacterioides, is a relative of the symbiont found in the vector for Chagas' disease that has been proven useful as a paratransgenic bacterium. Another isolate is a novel species within the gamma-proteobacteria that could not be phylogenetically placed within any of the known orders in the class but is close to a group of insect symbionts. Bacteria representing three intracellular genera were identified, among them the first identifications of Anaplasma species from mosquitoes and a new mosquito-Spiroplasma association. The isolates will be further investigated for their suitability for a paratransgenic Anopheles mosquito.

Feline hemotropic mycoplasmosis (feline hemobartonellosis)

Hemotropic mycoplasmas represent an important cause of anemia in cats worldwide. Previously known as Haemobartonella species, sequencing of the 16S rRNA genes of these organisms has led to their reclassification as mycoplasmas. Two species have been identified in cats, M haemofelis and "Candidatus M haemominutum." The latter organism alone has not been associated with disease in naturally infected cats but may cause anemia in FeLV-infected cats and accelerate development of FeLV-induced myeloproliferative disease. The mode of transmission of these organisms remains enigmatic. Nevertheless, development of sensitive DNA-based tests for these unculturable organisms has improved the understanding of the epidemiology and pathogenesis of FHM. Cats with clinical signs and laboratory abnormalities consistent with FHM should be treated with doxycycline; enrofloxacin may represent an effective alternative. Transfusion with packed red blood cells after cross-matching may be required for severely anemia cats, and addition of prednisone may be required if the diagnosis of FHM is uncertain, or response to antimicrobials alone is insufficient. Affected cats should be tested for FeLV, the most common concurrent infection in cats with FHM.

Use of a polymerase chain reaction assay to detect infection with Eperythrozoon wenyoni in cattle

OBJECTIVE

To determine whether a polymerase chain reaction (PCR) assay could be used to detect Eperythrozoon wenyoni in the blood of cattle.

DESIGN

Prospective study.

ANIMALS

95 cattle from various herds in Alabama and Georgia and 96 bulls enrolled in Auburn University's Alabama Beef Cattle Improvement Association Bull Test program.

PROCEDURE

Blood samples were collected by means of venipuncture of the median caudal vein and submitted for a CBC and PCR assay. Blood smears were made immediately after blood collection and examined by means of light microscopy.

RESULTS

Three of 95 cattle from herds in Alabama and Georgia and 5 of 96 bulls enrolled in the Bull Test program had positive PCR assay results. Organisms were seen in blood smears from only 5 of these 8 animals. Organisms were not seen in blood smears from any animals for which results of the PCR assay were negative.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that a PCR assay may be an effective method for detecting E wenyoni infection in cattle and that the PCR assay may be a more sensitive test than evaluation of blood smears.

Eperythrozoon ovis infection in a commercial flock of sheep

A flock of sheep consisting of 60-70 winterfed ewes was examined. Blood was collected from approximately 30% of the sheep four times from 1991 to 1995. Eperythrozoon ovis (Ep. ovis) organisms were not detected in blood smears stained with Wright's stain in 1991 and 1993. In 1995, examination of blood smears stained with acridine orange revealed Ep. ovis organisms in 11 of 26 sheep, whereas examination of smears stained with Wright's stain revealed organisms in only one ewe with a high degree of infection. The prevalence of antibodies detected by IFAT varied from 58-100%. The antibody titres varied from 1:20 to 1:12,000. This investigation indicates that Ep. ovis infection once present in a flock of sheep may spread easily among the sheep, and that the infection seems to persist within the flock.

Anaemia and low viability in piglets infected with Eperythrozoon suis

Eperythrozoon suis infection was identified in a pig herd during an investigation into anaemia and low viability in newborn piglets and severe regenerative macrocytic anaemia in older piglets. The organisms were identified in the erythrocytes of piglets a few days old. Extensive investigations failed to detect other causes of the anaemia and low viability. There was no response to parenteral iron administration alone but the piglets' viability and anaemia responded to the administration of tetracyclines. This is the first report of E suis infection in Northern Ireland.