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.

Detection of DNA of Babesia canis in tissues of laboratory rodents following oral inoculation with infected ticks

Background

Babesia spp. are apicomplexan parasites which infect a wide range of mammalian hosts. Historically, most Babesia species were described based on the assumed host specificity and morphological features of the intraerythrocytic stages. New DNA-based approaches challenge the traditional species concept and host specificity in Babesia. Using such tools, the presence of Babesia DNA was reported in non-specific mammalian hosts, including B. canis in feces and tissues of insectivorous bats, opening questions on alternative transmission routes. The aim of the present study was to evaluate if B. canis DNA can be detected in tissues of laboratory rodents following oral inoculation with infected ticks.

Methods

Seventy-five questing adult Dermacentor reticulatus ticks were longitudinally cut in two halves and pooled. Each pool consisted of halves of 5 ticks, resulting in two analogous sets. One pool set (n = 15) served for DNA extraction, while the other set (n = 15) was used for oral inoculation of experimental animals (Mus musculus, line CD-1 and Meriones unguiculatus). Blood was collected three times during the experiment (before the inoculation, at 14 days post-inoculation and at 30 days post-inoculation). All animals were euthanized 30 days post-inoculation. At necropsy, half of the heart, lung, liver, spleen and kidneys were collected from each animal. The presence of Babesia DNA targeting the 18S rRNA gene was evaluated from blood and tissues samples. For histopathology, the other halves of the tissues were used. Stained blood smears were used for the light microscopy detection of Babesia.

Results

From the 15 pools of D. reticulatus used for the oral inoculation, six were PCR-positive for B. canis. DNA of B. canis was detected in blood and tissues of 33.3% of the animals (4 out of 12) inoculated with a B. canis-positive pool. No Babesia DNA was detected in the other 18 animals which received B. canis-negative tick pools. No Babesia was detected during the histological examination and all blood smears were microscopically negative.

Conclusions

Our findings demonstrate that B. canis DNA can be detected in tissues of mammalian hosts following ingestion of infected ticks and opens the question of alternative transmission routes for piroplasms.

Short communication: Gut microbial colonization of the mouse colon using faecal transfer was equally effective when comparing rectal inoculation and oral inoculation based on 16S rRNA sequencing

In the present study we hypothesized that a higher degree of gut microbiota (GM) transfer and colonization could be reached by rectal inoculation compared to oral inoculation, which is commonly used in mouse studies for GM transfer. We treated C57BL/6NTac Specific Pathogen Free (SPF) mice with antibiotics and subsequently we inoculated these with GM from donor mice of the same strain by either the oral or the rectal inoculation method. 16S rRNA gene sequencing of the colon microbiota showed no difference in microbial community on account of inoculation method as determined by unweighted UniFrac distance metrics in C57BL/6NTac SPF mice. In addition, qPCR analysis on colon tissue revealed no difference in mRNA expression between the inoculation methods. Next, the SPF mice were compared to germ-free (GF)-mice to identify differences in inoculation efficacy. Whether the mice were antibiotic treated SPF or GF clearly influenced GM determined by 16S rRNA gene sequencing where the SPF mice experienced up-regulation of S24-7 (p = .0001) and a decrease in Rikenellaceae (p = .016) compared to GF mice. qPCR analysis on colon tissue revealed up-regulation in mRNA gene expression of Il6, Il10, Reg3g and transcription factor RORγt (Rorc) in GF mice compared to SPF mice on a significant level (p < .05). This gene expression profile is consistent with post colonization development of the intestinal barrier in GF mice.

Clinico-pathology and hemato-biochemistry responses in buffaloes infected with Pasteurella multocida type B:2 immunogen outer membrane protein

The aim of this study was to investigate the clinico-pathology and haemato-biochemistry alterations in buffaloes inoculated with Pasteurella multocida type B:2 immunogen outer membrane protein via subcutaneous and oral routes. Nine buffalo heifers were divided equally into 3 treatment groups. Group 1 was inoculated orally with 10 mL of phosphate buffer saline (PBS); Group 2 and 3 were inoculated with 10 mL of outer membrane protein broth subcutaneously and orally respectively. Group 2 buffaloes showed typical haemorrhagic septicaemia clinical signs and were only able to survive for 72 h of the experiment. However, Group 3 buffaloes were able to survive throughout the stipulated time of 21 days of experiment. There were significant differences (p < 0.05) in the rectal temperature between the experimental and control group. In the hematology and biochemistry findings, there were significant differences (p < 0.05) in packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin concentration, leukocytes, band neutrophils, segmented neutrophils, lymphocytes, eosinophils, basophils, gamma glutamyl transferase, total protein, and globulin between Group 2 and control group. In contrast, Group 3 and control group revealed significant differences (p < 0.05) in erythrocytes, haemoglobin, mean corpuscular haemoglobin concentration, segmented neutrophils, lymphocytes, monocytes, eosinophils, basophils, thrombocytes, gamma glutamyl transferase, total protein, globulin, and albumin:globulin ratio. In Group 2 buffaloes, there were gross lesions observed in the lung, trachea, heart, liver, spleen, kidney and submandibulae lymph nodes. In contrast, lesions were only observed in the lung, and liver of Group 3 buffaloes. There were significant differences (p < 0.05) in hemorrhage and congestion; necrosis and degeneration; and inflammatory cells infiltration between experimental groups and control group. However, there were no significant differences (p > 0.05) in edema between groups except for the lung. This study was a proof that oral route infection of Pasteurella multocida type B:2 immunogen outer membrane protein can be used to stimulate host cell.