The prevalence and infection rates of amphistome species in intermediate snail hosts: a systematic review and meta-analysis.

The systematic review and meta-analysis were conducted to determine the estimates of the prevalence and infection rates of natural and experimental infections of amphistome species in intermediate host snails (IHs) across different continents. A search of peer-reviewed literature on natural and experimental infections of freshwater snails with amphistome species was conducted from four electronic databases from 1984 to 2023. The estimates of the prevalence and/or infection rates were based on 36 eligible peer-reviewed articles, which met the inclusion criteria and reported on natural and experimental infections of amphistome species in freshwater snails. The results showed that a total of 1,67,081 snail species from the peer-reviewed articles were examined for natural infections and 7,659 snail species for experimental infections. The overall pooled prevalence of amphistome infections from naturally infected snails was 2% (95% CI: 0-4), while the overall pooled prevalence of amphistome infections from infections was 40% (95% CI: 18-64). The highest pooled prevalence of natural infection was 3%, which was recorded in Europe (95% CI: 1-7%). The highest overall prevalence of naturally infected amphistome was 6% (95% CI: 0-20%) for Paramphistomum epiclitum. The Americas had the highest pooled prevalence of experimental amphistome infection among freshwater snails (66%; 95% CI: 26-96%). The highest pooled infection rate of 65% (95% CI: 12-100%) was recorded for Paramphistomum cervi in experimental infections. Galba truncatula was the only snail that qualified for meta-analysis for natural infection with Calicophoron daubneyi, with a pooled prevalence of 3% (95% CI: 1-8%). Galba truncatula infected with C. daubneyi and P. cervi, and Bulinus tropicus infected with Calicophoron microbothrium in the experimental infection qualified for the meta-analysis, with an overall infection rate of 66% (95% CI: 34-92%) and 30% (95% CI: 0-74%), respectively. The pooled prevalence of amphistome species infection in the intermediate host (IH) snails based on detection techniques was higher with PCR compared to the dissection and shedding of cercariae. The results from the quality effects model revealed a high heterogeneity and publication bias between studies. This meta-analysis provided valuable insights into the prevalence and infection rates of amphistome species in snail IHs across different geographical regions.

Host specificity and virulence of Flavobacterium psychrophilum: a comparative study in ayu (Plecoglossus altivelis) and rainbow trout (Oncorhynchus mykiss) hosts.

Flavobacterium psychrophilum, the causative agent of bacterial cold-water disease, is a devastating, worldwide distributed, fish pathogen causing significant economic loss in inland fish farms. Previous epidemiological studies showed that prevalent clonal complexes (CC) differ in fish species affected with disease such as rainbow trout, coho salmon and ayu, indicating significant associations between particular F. psychrophilum genotypes and host species. Yet, whether the population structure is driven by the trade of fish and eggs or by host-specific pathogenicity is uncertain. Notably, all F. psychrophilum isolates retrieved from ayu belong to Type-3 O antigen (O-Ag) whereas only very few strains retrieved from other fish species possess this O-Ag, suggesting a role in outbreaks affecting ayu. Thus, we investigated the links between genotype and pathogenicity by conducting comparative bath infection challenges in two fish hosts, ayu and rainbow trout, for a collection of isolates representing different MLST genotypes and O-Ag. Highly virulent strains in one host species exhibited low to no virulence in the other. F. psychrophilum strains associated with ayu and possessing Type-3 O-Ag demonstrated significant variability in pathogenicity in ayu, ranging from avirulent to highly virulent. Strikingly, F. psychrophilum strains retrieved from rainbow trout and possessing the Type-3 O-Ag were virulent for rainbow trout but not for ayu, indicating that Type-3 O-Ag alone is not sufficient for pathogenicity in ayu, nor does it prevent pathogenicity in rainbow trout. This study revealed that the association between a particular CC and host species partly depends on the pathogen's adaptation to specific host species.

Exploring Variability: Inflammation Mediator Levels across Tissues and Time in Poultry Experimentally Infected by the G1a and G6 Genogroups of Infectious Bursal Disease Virus (IBDV).

Infectious bursal disease virus (IBDV) is a significant burden for poultry production and market due to both direct disease and induced immunosuppression. In the present study, the expression of different cytokines in the bursa of Fabricius and thymus was evaluated during a 28-day-long experimental infection with two strains classified in the G1a (Classical) and G6 (ITA) genogroups. Although both strains significantly affected and modulated the expression of different molecules, the G6 strain seemed to induce a delayed immune response or suppress it more promptly. A recovery in the expression of several mediators was observed in the G1a-infected group at the end of the study, but not in the G6 one, further supporting a more persistent immunosuppression. This evidence fits with the higher replication level previously reported for the G6 and with the clinical outcome, as this genotype, although subclinical, has often been considered more immunosuppressive. However, unlike other studies focused on shorter time periods after infection, the patterns observed in this paper were highly variable and complex, depending on the strain, tissue, and time point, and characterized by a non-negligible within-group variability. Besides confirming the strain/genogroup effect on immune system modulation, the present study suggests the usefulness of longer monitoring activities after experimental infection to better understand the complex patterns and interactions with the host response.

Ascaris Mouse Model Protocols: Advancing Research on Larval Ascariasis Biology.

Ascariasis, caused by both Ascaris lumbricoides and Ascaris suum, is the most prevalent parasitic disease worldwide, affecting both human and porcine populations. However, due to the difficulties of assessing the early events of infection in humans, most studies of human ascariasis have been restricted to the chronic intestinal phase. Therefore, the Ascaris mouse model has become a fundamental tool for investigating the immunobiology and pathogenesis of the early infection stage referred to as larval ascariasis because of the model's practicality and ability to replicate the natural processes involved. The Ascaris mouse model has been widely used to explore factors such as infection resistance/susceptibility, liver inflammation, lung immune-mediated pathology, and co-infections and, notably, as a pivotal element in preclinical vaccine trials. Exploring the immunobiology of larval ascariasis may offer new insights into disease development and provide a substantial understanding of key components that trigger a protective immune response. This article focuses on creating a comprehensive guide for conducting Ascaris experimental infections in the laboratory as a foundation for future research efforts. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Acquisition and embryonation of Ascaris suum eggs from adult females Alternate Protocol: Cleaning and purification of Ascaris suum from female A. suum uteri Basic Protocol 2: Preparation of Ascaris suum eggs and murine infection Basic Protocol 3: Measurement of larval burden and Ascaris-larva-induced pathogenesis Basic Protocol 4: In vitro hatching and purification of Ascaris L3 larvae Support Protocol: Preparation of crude antigen from Ascaris infectious stages Basic Protocol 5: Ultrastructure-expansion microscopy (U-ExM) of Ascaris suum larval stages.

Effect of Phlebotomus papatasi on the fitness,infectivity and antimony-resistance phenotype of antimony-resistant Leishmania major Mon-25.

Leishmania major is responsible for zoonotic cutaneous leishmaniasis. Therapy is mainly based on the use of antimony-based drugs; however, treatment failures and illness relapses were reported. Although studies were developed to understand mechanisms of drug resistance, the interactions of resistant parasites with their reservoir hosts and vectors remain poorly understood. Here we compared the development of two L. major MON-25 trivalent antimony-resistant lines, selected by a stepwise in vitro Sb(III)-drug pressure, to their wild-type parent line in the natural vector Phlebotomus papatasi. The intensity of infection, parasite location and morphological forms were compared by microscopy. Parasite growth curves and IC50 values have been determined before and after the passage in Ph. papatasi. qPCR was used to assess the amplification rates of some antimony-resistance gene markers. In the digestive tract of sand flies, Sb(III)-resistant lines developed similar infection rates as the wild-type lines during the early-stage infections, but significant differences were observed during the late-stage of the infections. Thus, on day 7 p. i., resistant lines showed lower representation of heavy infections with colonization of the stomodeal valve and lower percentage of metacyclic promastigote forms in comparison to wild-type strains. Observed differences between both resistant lines suggest that the level of Sb(III)-resistance negatively correlates with the quality of the development in the vector. Nevertheless, both resistant lines developed mature infections with the presence of infective metacyclic forms in almost half of infected sandflies. The passage of parasites through the sand fly guts does not significantly influence their capacity to multiply in vitro. The IC50 values and molecular analysis of antimony-resistance genes showed that the resistant phenotype of Sb(III)-resistant parasites is maintained after passage through the sand fly. Sb(III)-resistant lines of L. major MON-25 were able to produce mature infections in Ph. papatasi suggesting a possible circulation in the field using this vector.

Experimental inoculation of pigs with monkeypox virus results in productive infection and transmission to sentinels.

Monkeypox virus (MPXV) is a re-emerging zoonotic poxvirus responsible for producing skin lesions in humans. Endemic in sub-Saharan Africa, the 2022 outbreak with a clade IIb strain has resulted in ongoing sustained transmission of the virus worldwide. MPXV has a relatively wide host range, with infections reported in rodent and non-human primate species. However, the susceptibility of many domestic livestock species remains unknown. Here, we report on a susceptibility/transmission study in domestic pigs that were experimentally inoculated with a 2022 MPXV clade IIb isolate or served as sentinel contact control animals. Several principal-infected and sentinel contact control pigs developed minor lesions near the lips and nose starting at 12 through 18 days post-challenge (DPC). No virus was isolated and no viral DNA was detected from the lesions; however, MPXV antigen was detected by IHC in tissue from a pustule of a principal infected pig. Viral DNA and infectious virus were detected in nasal and oral swabs up to 14 DPC, with peak titers observed at 7 DPC. Viral DNA was also detected in nasal tissues or skin collected from two principal-infected animals at 7 DPC post-mortem. Furthermore, all principal-infected and sentinel control animals enrolled in the study seroconverted. In conclusion, we provide the first evidence that domestic pigs are susceptible to experimental MPXV infection and can transmit the virus to contact animals.

Australian vertebrate hosts of Japanese encephalitis virus; a review of the evidence.

Japanese Encephalitis Virus (JEV) transmission in temperate Australia has underscored a critical need to characterise transmission pathways and identify probable hosts of infection within the country. This systematic review consolidates existing research on the vertebrate hosts of JEV that are known to exist in Australia. Specifically, we aim to identify probable species for JEV transmission, their potential role as either a spillover or maintenance host and identify critical knowledge gaps. Data were extracted from studies involving experimental infection, seroprevalence, and virus isolation and were available for 22 vertebrate species known to reside in Australia. A host competence score was calculated to assess the potential for a given species to infect JEV vectors and to quantity their possible role in JEV transmission. Based on the host competence score and ecology of each species, we find ardeid birds, feral pigs, and flying foxes have potential as maintenance hosts for JEV in the Australian context. We also note that brushtail possums and domestic pigs have potential as spillover hosts under certain outbreak conditions. However, evidence to confirm these roles in localized transmission or outbreaks is sparse, emphasizing the need for further targeted research. This review provides a foundation for future investigations into JEV transmission in Australia, advocating for enhanced surveillance and standardized research methodologies to better understand and mitigate the virus's impact.

The prospects of automation in drug discovery research using silkworms.

We have established several models of infectious diseases in silkworms to explore disease-causing mechanisms and identify new antimicrobial substances. These models involve injecting laboratory-cultured pathogens into silkworms and monitoring their survival over a period of days. The use of silkworms is advantageous because they are cost-effective and raise fewer ethical concerns than mammalian subjects, allowing for larger experimental group sizes. To capitalize on these benefits, there is a growing importance in mechanizing and automating the experimental processes that currently require manual labor. This paper discusses the future of laboratory automation, specifically through the mechanization and automation of silkworm-based experimental procedures.

Experimental Susceptibility of Nyssomyia antunesi and Lutzomyia longipalpis (Psychodidae: Phlebotominae) to Leishmania (Viannia) lainsoni and L. (V.) lindenbergi (Trypanosomatidae: Leishmaniinae).

The present work assessed the experimental susceptibility of Nyssomyia antunesi and Lutzomyia longipalpis to Leishmania (Viannia) lainsoni and L. (V.) lindenbergi. A L. (Leishmania) chagasi-Lu. longipalpis combination was used as a susceptible control. Wild-caught Ny. antunesi and laboratory-bred Lu. longipalpis were membrane-fed on blood with a 5 × 106/mL log-phase promastigote culture suspension and dissected on days 2 and 8 post-blood meal (pbm) for analysis focused on the assessment of parasitoses, as well as placement and promastigote morphotyping. Survival curves were constructed. In all combinations, promastigotes were observed on day 8 pbm. For both Leishmania species, in Lu. longipalpis, the presence of parasites was observed up to the stomodeal valve, while in Ny. antunesi, the presence of parasites was observed up to the cardia. There were no significant differences in parasitosis between L. (V.) lainsoni and L. (V.) lindenbergi in either Ny. antunesi or Lu. longipalpis. Six morphological promastigote forms were distinguished in Giemsa-stained gut smears. The survival curves of all combinations decreased and were affected differently by several Lu. longipalpis-parasite combinations, as well with Lu. longipalpis-uninfected blood. These findings stress Lu. longipalpis as experimentally susceptible to Leishmania spp. and suggest the putative susceptibility of Ny. antunesi to L. (V.) lainsoni and L. (V.) lindenbergi.

Inflammation, the kynurenines, and mucosal injury during human experimental enterotoxigenic Escherichia coli infection.

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrhea in children and travelers, especially in low- and middle-income countries. ETEC is a non-invasive gut pathogen colonizing the small intestinal wall before secreting diarrhea-inducing enterotoxins. We sought to investigate the impact of ETEC infection on local and systemic host defenses by examining plasma markers of inflammation and mucosal injury as well as kynurenine pathway metabolites. Plasma samples from 21 volunteers experimentally infected with ETEC were collected before and 1, 2, 3, and 7 days after ingesting the ETEC dose, and grouped based on the level of intestinal ETEC proliferation: 14 volunteers experienced substantial proliferation (SP) and 7 had low proliferation (LP). Plasma markers of inflammation, kynurenine pathway metabolites, and related cofactors (vitamins B2 and B6) were quantified using targeted mass spectrometry, whereas ELISA was used to quantify the mucosal injury markers, regenerating islet-derived protein 3A (Reg3a), and intestinal fatty acid-binding protein 2 (iFABP). We observed increased concentrations of plasma C-reactive protein (CRP), serum amyloid A (SAA), neopterin, kynurenine/tryptophan ratio (KTR), and Reg3a in the SP group following dose ingestion. Vitamin B6 forms, pyridoxal 5'-phosphate and pyridoxal, decreased over time in the SP group. CRP, SAA, and pyridoxic acid ratio correlated with ETEC proliferation levels. The changes following experimental ETEC infection indicate that ETEC, despite causing a non-invasive infection, induces systemic inflammation and mucosal injury when proliferating substantially, even in cases without diarrhea. It is conceivable that ETEC infections, especially when repeated, contribute to negative health impacts on children in ETEC endemic areas.

Growth hormone stimulates the in vitro development and establishment of Haemonchus contortus in sheep.

The physiologic increase in some sex hormones has been associated with an increase in the parasite load caused by Haemonchus contortus in ewes, especially prolactin. In lambs that are especially susceptible to hemonchosis, the levels of sex hormones are low; in contrast, the levels of another pituitary hormone, growth hormone (GH), which is structurally very similar to prolactin, are high. In this study, the in vitro and in vivo effects of GH on H. contortus larvae development and establishment were evaluated. The addition of 20 ng/mL GH for 5 and 10 days to cultures of H. contortus larvae induced an enlargement (p<0.01) and an L3/L4 molting rate (p<0.03) greater than that of untreated larvae or those treated with other concentrations of the hormone. Flow cytometry showed that 3.8% of the largest and most complex cells of newly obtained larvae of H. contortus were positive for the GH receptor, and by immunofluorescence with confocal microscopy, it was observed that these receptors are located in the intestinal region larvae. In the in vivo assay, the administration of recombinant GH to gonadectomized lambs produced an increase in FEC (p<0.03), the number of female adult worms in the abomasum (p<0.05) and the levels of specific antibodies (p<0.04) in relation to the control lambs; however, it did not affect the fertility of H. contortus females. Although many factors affect the development and implantation of H. contortus in the abomasum of sheep, the results of this study strongly suggest that GH participates in the development and establishment of the parasite in sheep, mainly in young sheep.

Genetic diversity of Cryptosporidium spp., Encephalitozoon spp. and Enterocytozoon bieneusi in feral and captive pigeons in Central Europe.

Cryptosporidium spp., Enterocytozoon bieneusi and Encephalitozoon spp. are the most common protistan parasites of vertebrates. The results show that pigeon populations in Central Europe are parasitised by different species of Cryptosporidium and genotypes of microsporidia of the genera Enterocytozoon and Encephalitozoon. A total of 634 and 306 faecal samples of captive and feral pigeons (Columba livia f. domestica) from 44 locations in the Czech Republic, Slovakia and Poland were analysed for the presence of parasites by microscopy and PCR/sequence analysis of small subunit ribosomal RNA (18S rDNA), 60 kDa glycoprotein (gp60) and internal transcribed spacer (ITS) of SSU rDNA. Phylogenetic analyses revealed the presence of C. meleagridis, C. baileyi, C. parvum, C. andersoni, C. muris, C. galli and C. ornithophilus, E. hellem genotype 1A and 2B, E. cuniculi genotype I and II and E. bieneusi genotype Peru 6, CHN-F1, D, Peru 8, Type IV, ZY37, E, CHN4, SCF2 and WR4. Captive pigeons were significantly more frequently parasitised with screened parasite than feral pigeons. Cryptosporidium meleagridis IIIa and a new subtype IIIl have been described, the oocysts of which are not infectious to immunodeficient mice, whereas chickens are susceptible. This investigation demonstrates that pigeons can be hosts to numerous species, genotypes and subtypes of the studied parasites. Consequently, they represent a potential source of infection for both livestock and humans.

Assessing the Risk of Dengue Virus Local Transmission: Study on Vector Competence of Italian Aedes albopictus.

The frequency of locally transmitted dengue virus (DENV) infections has increased in Europe in recent years, facilitated by the invasive mosquito species Aedes albopictus, which is well established in a large area of Europe. In Italy, the first indigenous dengue outbreak was reported in August 2020 with 11 locally acquired cases in the Veneto region (northeast Italy), caused by a DENV-1 viral strain closely related to a previously described strain circulating in Singapore and China. In this study, we evaluated the vector competence of two Italian populations of Ae. albopictus compared to an Ae. aegypti lab colony. We performed experimental infections using a DENV-1 strain that is phylogenetically close to the strain responsible for the 2020 Italian autochthonous outbreak. Our results showed that local Ae. albopictus is susceptible to infection and is able to transmit the virus, confirming the relevant risk of possible outbreaks starting from an imported case.

Experimental infection of goats with Mycobacterium microti induces subclinical pulmonary tuberculosis and mild responses to tuberculin skin tests.

Mycobacterium microti is a member of the Mycobacterium tuberculosis complex that seldom causes disease in livestock and humans. This study evaluated the effects on immunodiagnosis and the pathological findings in goats after experimental exposure by different routes and doses to M. microti. In a first experiment goats were challenged orally (PO, n = 7) or intranasally (IN, n = 7) with 104 CFU. In a second experiment, the endobronchial route was assessed, with a low dose of 102 CFU (EB-LD, n = 7) and a high dose of 105 CFU (EB-HD, n = 7) as well as the subcutaneous route (SC, n = 5). Temperature, body weight, clinical signs and immunological responses were monitored. Pathological evaluation was carried out and samples were processed for mycobacterial detection. RESULTS: demonstrated the induction of a subclinical pulmonary infection in all the EB-HD challenged animals. Infection was also confirmed in one animal of the SC group, but not in the EB-LD, PO or IN groups. Two animals belonging to the EB-HD and SC groups, respectively, showed positive results to the single intradermal tuberculin test, and another two animals of the EB-HD and EB-LD groups showed doubtful (inconclusive) results, indicating that M. microti can induce mild responses to tuberculin skin testing. No positive results were observed when defined antigens absent in M. microti (ESAT-6 and CPF-10) were used. Our results indicate that animals exposed to M. microti can yield positive results to the skin tests currently performed in livestock tuberculosis eradication campaigns and reinforce the need to use specific antigens in antemortem tests to avoid interference with M. bovis/M. caprae diagnosis.

Experimental co-infection of calves with SARS-CoV-2 Delta and Omicron variants of concern.

Since emerging in late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has repeatedly crossed the species barrier with natural infections reported in various domestic and wild animal species. The emergence and global spread of SARS-CoV-2 variants of concern (VOCs) has expanded the range of susceptible host species. Previous experimental infection studies in cattle using Wuhan-like SARS-CoV-2 isolates suggested that cattle were not likely amplifying hosts for SARS-CoV-2. However, SARS-CoV-2 sero- and RNA-positive cattle have since been identified in Europe, India, and Africa. Here, we investigated the susceptibility and transmission of the Delta and Omicron SARS-CoV-2 VOCs in cattle. Eight Holstein calves were co-infected orally and intranasally with a mixed inoculum of SARS-CoV-2 VOCs Delta and Omicron BA.2. Twenty-four hours post-challenge, two sentinel calves were introduced to evaluate virus transmission. The co-infection resulted in a high proportion of calves shedding SARS-CoV-2 RNA at 1- and 2-days post-challenge (DPC). Extensive tissue distribution of SARS-CoV-2 RNA was observed at 3 and 7 DPC and infectious virus was recovered from two calves at 3 DPC. Next-generation sequencing revealed that only the SARS-CoV-2 Delta variant was detected in clinical samples and tissues. Similar to previous experimental infection studies in cattle, we observed only limited seroconversion and no clear evidence of transmission to sentinel calves. Together, our findings suggest that cattle are more permissive to infection with SARS-CoV-2 Delta than Omicron BA.2 and Wuhan-like isolates but, in the absence of horizontal transmission, are not likely to be reservoir hosts for currently circulating SARS-CoV-2 variants.

Pathogenicity assessment of a bovine viral diarrhea virus type 1l (BVDV-1l) strain in experimentally infected calves.

Bovine viral diarrhea is a widespread and economically important viral disease for livestock which can cause clinically diverse manifestations. The number of established BVDV subgenotypes has increased, not only the serological relationships of recently described subgenotypes but virulence and pathogenic characteristics have not yet been mostly elaborated. The dominant BVDV subgenotype in Turkiye was elaborated to be BVDV-1l, that involves more than half of field strains and there is no scientific data to identify the pathogenicity of this strain so far. This study investigated the pathogenicity of a selected field strain (TR-72) from subgenotype BVDV-1l. Experimental infection was implemented by intranasal inoculation of the strain TR-72 (10 ×105.5) to four young calves which were previously not vaccinated and were free both for BVDV antibodies and antigens. Clinical changes as well as blood parameters, body temperature, and viremia were monitored for 14 days. Only mild clinical signs associated with respiratory signs of BVDV infection were observed. Detected clinical signs included nasal discharge, conjunctivitis, cough, fatigue, high rectal temperature reaching 40.7 â„ƒ, and white blood cell counts depression started from the 2nd day and 40.4% decreased between the 12th and 14th days post-infection (poi). The presence of viremia was investigated by virus isolation, RT-PCR, and real-time RT-PCR from blood samples. The efficiency of experimental infection was established not only by observed clinical signs but also by virus isolation from blood leukocytes between the 5th and 8th days poi., virus detection was obtained by real-time PCR between the 3rd - 13th days poi. Besides, the recorded mild clinical signs, high fever, long duration of viremia , and high decrease in blood parameters obtained in this study, it was shown that the noncytopathogenic BVDV-1l strain TR-72 has a moderate virulence in naïve cattle.

Modeling Paratuberculosis in Laboratory Animals, Cells, or Tissues: A Focus on Their Applications for Pathogenesis, Diagnosis, Vaccines, and Therapy Studies.

Paratuberculosis is a chronic granulomatous enteritis caused by Mycobacterium avium subsp. Paratuberculosis that affects a wide variety of domestic and wild animals. It is considered one of the diseases with the highest economic impact on the ruminant industry. Despite many efforts and intensive research, paratuberculosis control still remains controversial, and the existing diagnostic and immunoprophylactic tools have great limitations. Thus, models play a crucial role in understanding the pathogenesis of infection and disease, and in testing novel vaccine candidates. Ruminant animal models can be restricted by several reasons, related to space requirements, the cost of the animals, and the maintenance of the facilities. Therefore, we review the potential and limitations of the different experimental approaches currently used in paratuberculosis research, focusing on laboratory animals and cell-based models. The aim of this review is to offer a vision of the models that have been used, and what has been achieved or discovered with each one, so that the reader can choose the best model to answer their scientific questions and prove their hypotheses. Also, we bring forward new approaches that we consider worth exploring in the near future.

Experimental infection of non-immunosuppressed and immunosuppressed goats reveals differential pathogenesis of Babesia aktasi n. sp.

Babesiosis is an acute and persistent tick-borne disease caused by protozoan parasites of the genus Babesia. These hemoparasites affect vertebrates globally, resulting in symptoms such as high fever, anemia, jaundice, and even death. Advancements in molecular parasitology revealed new Babesia species/genotypes affecting sheep and goats, including Babesia aktasi n. sp., which is highly prevalent in goats from Turkiye's Mediterranean region. The objective of this study was to investigate the pathogenesis of B. aktasi infection in immunosuppressed (n=7) and non-immunosuppressed (n=6) goats. These animals were experimentally infected with fresh B. aktasi infected blood, and their clinical signs, hematological and serum biochemical parameters were monitored throughout the infection. The presence of parasites in the blood of immunosuppressed goats was detected by microscopic examination between 4 and 6 days after infection, accompanied by fever and increasing parasitemia. Goats that succumbed acute disease exhibited severe clinical signs, such as anemia, hemoglobinuria, and loss of appetite. However, the goats that survived showed milder clinical signs. In the non-immunosuppressed group, piroplasm forms of B. aktasi were observed in the blood within 2-5 days after inoculation, but with low (0.01-0.2%) parasitemia. Although these goats showed loss of appetite, typical signs of babesiosis were absent except for increased body temperature. Hematological analysis revealed significant decreases in the levels of red blood cells, leukocytes and platelet values post-infection in immunosuppressed goats, while no significant hematological changes were observed in non-immunosuppressed goats. In addition, serum biochemical analysis showed elevated transaminase liver enzymes levels, decreased glucose, and lower total protein values in the immunosuppressed group post-infection. Babesia aktasi, caused mild disease with minor clinical symptoms in non-immunosuppressed goats. However, in immunosuppressed goats, it exhibited remarkable pathogenicity, leading to severe clinical infections and death. In conclusion, this study provides valuable insights into the pathogenicity of the parasite and will serve as a foundation for future research aimed at developing effective prevention and control strategies against babesiosis in small ruminants. Further research is required to investigate the pathogenicity of B. aktasi in various goat breeds, other potential hosts, the vector ticks involved, and its presence in natural reservoirs.

A critical review on experimental Streptococcus suis infection in pigs with a focus on clinical monitoring and refinement strategies.

Streptococcus suis (S. suis) is a major pig pathogen worldwide with zoonotic potential. Though different research groups have contributed to a better understanding of the pathogenesis of S. suis infections in recent years, there are still numerous neglected research topics requiring animal infection trials. Of note, animal experiments are crucial to develop a cross-protective vaccine which is highly needed in the field. Due to the severe clinical signs associated with S. suis pathologies such as meningitis and arthritis, implementation of refinement is very important to reduce pain and distress of experimentally infected pigs. This review highlights the great diversity of clinical signs and courses of disease after experimental S. suis pig infections. We review clinical read out parameters and refinement strategies in experimental S. suis pig infections published between 2000 and 2021. Currently, substantial differences exist in describing clinical monitoring and humane endpoints. Most of the reviewed studies set the body temperature threshold of fever as high as 40.5°C. Monitoring intervals vary mainly between daily, twice a day and three times a day. Only a few studies apply scoring systems. Published scoring systems are inconsistent in their inclusion of parameters such as body temperature, feeding behavior, and respiratory signs. Locomotion and central nervous system signs are more common clinical scoring parameters in different studies by various research groups. As the heterogenicity in clinical monitoring limits the comparability between studies we hope to initiate a discussion with this review leading to an agreement on clinical read out parameters and monitoring intervals among S. suis research groups.

Experimental infection and co-infection with Chinese strains of Ehrlichia canis and Babesia vogeli in intact and splenectomized dogs: Insights on clinical, hematologic and treatment responses.

Animal infection models are crucial for studying various aspects of Ehrlichia canis infections. To understand the pathogenesis of the first Chinese isolate of E. canis and simulate the natural progression of canine ehrlichiosis, we developed a model with 18 Beagle dogs that consisted of E. canis initial infection (days 0-17), treatment with doxycycline or rifampicin (days 18-32), recovery (days 33-66), E. canis reinfection (days 67-91), and Babesia vogeli superinfection (days 92-116). We measured body weight and rectal temperature every other day, drew blood every 4 days for routine hematology and biochemistry tests, and for quantification of E. canis and B. vogeli by quantitative PCRs. In this study, the first isolate of E. canis from China was used to experimentally infect dogs, and the infected dogs exhibited clinical signs of acute severe ehrlichiosis, including high fever, loss of appetite, dehydration, and body weight loss, confirming the similar pathogenicity of E. canis in China as compared to isolates from other regions. Infection with E. canis and B. vogeli led to reduced body weight and fever in dogs. Doxycycline treatment led to absence of E. canis DNA in infected dogs, while rifampicin treatment lowered the blood E. canis copy number up to 1.5 folds. E. canis-free infected dogs after doxycycline treatment were successfully re-infected with E. canis, indicating dogs with antibodies are still at risk of re-infection. Super-infection with B. vogeli resulted in higher fever, more severe anemia, and a reduced number of platelets. Splenectomized dogs showed significantly higher E. canis numbers during recovery and re-infection than intact dogs. The histological changes were observed in brain, lung, kidney, liver and spleen of the infected dogs. The findings in this study provide insights into clinical and hematologic responses, as well as effective treatment options, for dogs infected with the first Chinese isolate of E. canis, and may contribute to our understanding of the diagnosis and prevention of tick-borne diseases in dogs, including canine monocytic ehrlichiosis.