The use of analgesia in bacterial challenge models has been met with some controversy in the literature. Several publications suggest that the use of analgesics in infection models can interfere with the host immune response, change microenvironments subsequently altering bacterial pathogenesis, and directly act as an antimicrobial as was reported with opioids such as morphine. Any such interactions would compromise the experimental results, deterring researchers from the use of analgesia. Herein, we address the possible effect of analgesics on bacterial colonization in a Staphylococcus aureus surgical site infection model in G & ouml;ttingen minipigs. Retrospectively, an expanded analgesia protocol (buprenorphine presurgery and carprofen postsurgery) was compared with a standard analgesia protocol using buprenorphine alone just before surgery. When examined statistically, the expanded analgesia protocol group was noninferior to the standard analgesia protocol group indicating there was no substantial decrease in bacterial burden when an expanded analgesia protocol was administered. Our results highlight the importance of studying the use of analgesia in all animal models of infection to determine if the analgesics will affect experimental outcomes.
Enterovirus D68 (EV-D68) causes severe respiratory disease and is a strong candidate as the etiologic agent of acute flaccid myelitis. Acute flaccid myelitis is a rare neurologic disorder that typically affects adolescents less than 13 y old, manifesting as muscle paralysis or weakness. No approved antiviral compounds or vaccines exist for EV-D68. An appropriate mouse model is needed to develop therapeutics. We previously showed that the AG129 mouse strain, which has a double knockout of Ifnar1 and Ifngr1 on the 129/Sv genetic background, exhibits clear clinical signs when infected intraperitoneally with EV-D68 at postnatal day 10. The AGB6 strain, which has the same double knockout, but on the C57BL/6 (B6) genetic background, is more sensitive to dengue virus infections relative to AG129. Given the widespread use of the B6 background in mouse research, we systematically assessed EV-D68 infection in AGB6, the AB6 and GB6 strains, which have single knockouts in Ifnar1 and Ifngr1, respectively, and the parental B6 strain. AGB6 was highly susceptible to EV-D68, equivalent to AG129. No differences in susceptibility were observed between AGB6 and AB6 and GB6 and B6, suggesting that the IFN gamma receptor contributes little to EV-D68 protection. Because B6 is the genetic background for many genetically modified mice, AGB6 facilitates the evaluation of the role of host genes in EV-D68 pathogenesis through genetic crosses. We introduced the knockout allele of Setd3, a gene essential for enterovirus RNA replication, into AGB6. While EV-D68 lethality was completely penetrant in AGB6-Setd3+/+ and AGB6-Setd3+/- mice, all AGB6-Setd3-/- littermates survived until the experimental endpoint. We conclude that AGB6 is well suited for testing EV-D68 therapeutics. Our study further underscores the importance of SETD3 being a promising therapeutic target for controlling EV-D68 and other enterovirus infections.
The congenic BALB/c-crup (‘crup’ meaning ‘cruza-pernas’ in Portuguese or cross legs in English), a homozygous recessive mutant mouse derived from N-ethyl-N-nitrosourea mutagenesis, exhibits a unique phenotype characterized by hindlimb crossing when the mouse is suspended by its tail, along with age-related neuromotor issues. The study aimed to identify the genetic mutation causing the BALB/c-crup phenotype and evaluate the behavioral responses of the mice. Open field test, elevated plus maze, and elevated beam experiments were conducted to evaluate general activity, motor function, as well as sensorimotor and autonomic nervous systems. Genetic mapping and exome analysis identified a nonsynonymous (missense mutation), a single nucleotide variant, in the Taf15 gene. This mutation results in the p.G55S substitution, where glycine is replaced by serine at position 55 in the gene product. Longitudinal assessment by the open field test revealed altered locomotion, decreased mobility, and reduced rearing and grooming frequency in mutant mice. Sensorimotor function declines were observed through reduced surface righting reflex scores, grip strength, and increased hindquarter angle. In the elevated beam test, mutants exhibited tail hypotonia and aversion to traversing the beam. The elevated plus maze revealed altered behavior in closed arms, suggesting increased anxiety-like behavior or sensorimotor impairment. Our findings provide insights into neurologic and behavioral anomalies associated with a Taf15 gene mutation. The altered locomotion, sensory impairments, and disorientation observed in the crup phenotype indicate a progressive neuromotor condition, potentially serving as a novel mouse model for neurodegenerative diseases.
Mouse kidney parvovirus (MKPV) infection can cause significant morbidity and mortality by inducing moderate to severe inclusion body nephropathy and kidney fibrosis in aged immunodeficient mice. However, MKPV infection in immunocompetent mice is associated with histopathologic findings ranging from absent to minimal or moderate lymphoplasmacytic interstitial nephritis without inclusion body in most cases. We surveyed the prevalence of MKPV via PCR from August 2019 through January 2021, using feces, kidneys, and livers collected and pooled from 2 sentinel mice [Crl:CD1(ICR)] (CD1) per surveillance cage (a total of 212 cages). CD1 mice used as dirty-bedding sentinels were housed for 6 mo in a separate cage on the same rack as colony mice used in research at the Massachusetts Institute of Technology and at the Whitehead Institute for Biomedical Research. MKPV quantitative PCR positivity was 16.04%, 14.62%, and 10.02% for feces, kidney, and liver, respectively. The aggregate prevalence of MKPV was 22.64% (48 of 212 samples). Thirty-three of 103 rooms (32.04%) were MKPV positive. MKPV-positive kidneys had more severe chronic lymphoplasmacytic interstitial nephritis (CLIN) than MKPV-negative kidneys; however, there was no significant difference in hepatic lesions between MKPV-positive and -negative livers. Although no overt intranuclear inclusion body nephropathy was noted in MKPV-positive CD1 kidneys, MKPV RNA was sporadically detected within tubular epithelial cells in MKPV-positive kidneys but not in MKPV-positive livers. Our study indicates that MKPV can be easily transmitted through soiled bedding. It highlights that CD1 mice can be used as sentinels to detect MKPV, emphasizing the importance of monitoring MKPV distribution using quantitative PCR in sentinel mice if MKPV needs to be excluded from a colony. Importantly, as MKPV infection is associated with mild to moderate CLIN, MKPV can potentially confound the interpretation of in vivo biomedical data.
Due to their hematophagous life cycle, hard-bodied ticks including the genus Ixodes are a potential vector for numerous pathogenic organisms including bacteria, protozoa, viruses, and infectious prions. The natural geographic range of several hard tick species, includig Ixodes scapularis, has expanded over recent decades. Consequently, there is an ongoing need to maintain, feed, and propagate ticks for host-pathogen interaction studies to better understand and mitigate their impact on human and animal health. Artificial membrane feeding of hard ticks has advanced in recent years, has study design advantages, and should be used, when possible, to reduce animal use, but it also has several limitations that require the continued use of mammalian hosts including mice, guinea pigs, and rabbits. In this overview, we discuss the best management practices for these relevant species with respect to biosafety, health, and optimal host comfort when used in studies that depend on tick feeding. The capsule-jacket method is preferred over the ear sock-E-collar method of tick feeding on rabbit hosts because of better host health, comfort, and increased study versatility.
The fetal sheep model has been widely used in fetal therapy research. However, there is a significant degree of variability among published normal values. Our study aimed to evaluate the literature available on normal values for hemodynamics, blood gases, and acid-base status in the sheep fetus and to determine the best possible estimation of such physiologic values. We conducted a systematic review with a comprehensive search of several databases. We included 189 articles in the database and over 2,800 sheep fetuses. Analysis revealed a mean umbilical blood flow of 202 mL/kg/min (95% CI: 182 to 223); mean arterial pCO2 of 49.8 mm Hg (95% CI: 49.2 to 50.3); mean arterial pO2 of 22.3 mm Hg (95% CI: 21.9 to 22.7); mean arterial pH of 7.35 (95% CI: 7.3487 to 7.3562); and mean arterial oxygen saturation of 59.8 (95% CI; 58 to 61.7). Our findings were punctuated by a high heterogeneity, for which we conducted several subanalyses. The results showed high heterogeneity and small study effect in the literature available and provided our best assessment of relevant variables on normal hemodynamics, blood gases, and acid-base status in the fetus after using strategies to mitigate the risk of bias present in the literature.
Pain management in amphibians is an emerging field of veterinary medicine with only a limited number of analgesics studied for their efficacy. The African-clawed frog, Xenopus laevis , is a popular animal model in research due to its oocyte morphology and embryonic development. We investigated analgesic effects of 2 formulations of meloxicam (standard and extended release [ER]) along with their pharmacokinetics and potential toxicity in this species. Adult female African-clawed frogs ( n = 6/group) received either standard (0.2, 0.4, 1, or 5 mg/kg) or ER meloxicam (0.6, 1.2, 3, or 15 mg/kg) injected into the dorsal lymph sac. The acetic acid test (AAT) was performed at -1, 1, 6, 12, 24, 48, and 72 h postadministration to evaluate pain response. In addition, a subset of frogs ( n = 2/group) were euthanized 72 h postinjection and submitted for necropsy. There were no significant differences in AAT with both formulations compared with saline control. No signs of meloxicam-induced toxicity with either formulation was present in histology. A pharmacokinetic study was conducted for both the standard and ER formulation of meloxicam at 5 and 15 mg/kg, respectively. Results were consistent with the fact that both formulations of meloxicam were readily absorbed with the standard plasma concentrations peaking at 20.40 µg/mL at 2 h and ER plasma concentration at 30.4 µg/mL at 12 h. The elimination half-life was only determinable for standard formulation (7.74 h). According to the AAT, both formulations of meloxicam did not provide effective analgesia in adult female Xenopus laevis despite reaching high plasma concentrations.
Experimental maxillofacial surgery is commonly performed in pigs; however, locoregional anesthesia of this area has not been described. This study evaluated the feasibility of a novel maxillary nerve block approach. In part I, cadavers were used to determine anatomic landmarks and assess maxillary nerve dye staining by using 0.03 mL kg −1 of a 1:10 mixture of commercial food dye and 0.5% bupivacaine. In part II, 10 additional pig cadavers underwent bilateral ultrasound-guided maxillary nerve blocks by using trans-infraorbital canal needle placement. The maxillary nerve was harvested and scored based on degree of staining (0 and 1, absent or incomplete staining; 2, staining; >1 cm circumferentially). Intracranial and intraconal spread of dye was evaluated. A Kruskal–Wallis test was used to compare infraorbital canal length estimated either externally via landmarks, internally via ultrasound, or actually measured after dissection. In 18 of 20 (90%) injections, successful staining (score = 2) of maxillary nerves was obtained for a nerve length of 2.4 ± 0.3 cm. Two of 20 cases (10%) had inadequate staining (score <2). At dissection of these 2 cases, the needle tip was observed to have collided with an unerupted tooth (third molar). No intracranial or intraconal spread of dye was observed. We detected no statistical differences between the estimated external, estimated internal, or actual dissection methods for measurement of infraorbital canal length ( P = 0.3). Ultrasound-guided trans-infraorbital maxillary nerve block in pigs is a feasible technique, warranting further work to evaluate its in vivo efficacy and safety.
Enterovirus D68 (EV-D68), a respiratory RNA virus in the family Picornaviridae, is implicated as a potential etiological agent for acute flaccid myelitis in preteen adolescents. The absence of a specific therapeutic intervention necessitates the development of an effective animal model for EV-D68. The AG129 mouse strain, characterized by the double knockout of IFN-α/β and IFN-γ receptors on the 129 genetic background, has been proposed as a suitable model for EV-D68. The goals of this study were to assess the effect of a nonmouse-adapted EV-D68 strain (US/MO/14-18947, NR-49129) in AG129 (IFN-α/β and IFN-γ receptors null), A129 (IFN-α/β receptor null), G129 (IFN-γ receptor null), and the 129 background strain (129S2/SvPasCrl) when infected intraperitoneally at 10 d of age. Both AG129 and A129 strains demonstrated similar clinical signs (paralysis, paresis, lethargy, dyspnea [characterized by prominent abdominal respiration], and morbidity requiring euthanasia) induced by EV-D68. While G129 and 129S2 strains also exhibited susceptibility to EV-D68, the severity of clinical signs was less than in AG129 and A129 strains, and many survived to the experimental endpoint. Histopathological and immunohistochemical data confirmed EV-D68 tropism for the skeletal muscle and spinal cord and suggest that the dyspnea observed in infected mice could be attributed, in part, to lesions in the diaphragmatic skeletal muscles. These findings contribute valuable insights into the pathogenesis of EV-D68 infection in this mouse model and provide investigators with key information on virus dose and mouse strain selection when using this mouse model to evaluate candidate EV-D68 therapeutics.
Whole blood analysis can evaluate numerous parameters, including pH, pCO2, pO2, HCO3 -, base excess, glucose, electrolytes, lactate, blood urea nitrogen, creatinine, bilirubin, and hemoglobin. This valuable tool enables clinicians to make more informed decisions about patient care. However, the current body of literature describing perioperative whole blood analysis in Dorset sheep (Ovis aries) is small, so clinicians lack adequate information to guide their decision-making when evaluating test results. We evaluated arterial and venous whole blood pH, bicarbonate, pCO2, lactate, creatinine, and blood urea nitrogen before and for the first 24 hours after surgery in 2 cohorts of male and female Ovis aries undergoing one of 2 major cardiovascular procedures, a Single-Stage Fontan or an inferior vena cava to pulmonary artery extracardiac conduit implantation (IP-ECC). The cohort undergoing a Single-Stage Fontan, which is the more complex procedure, exhibited greater deviation from baseline measurements than did the cohort undergoing the IP-ECC for lactate, bicarbonate, and creatinine. The cohort undergoing the IP-ECC showed no significant deviation from baseline for any parameters, potentially indicating a better safety margin than expected when compared with the Single-Stage Fontan. Together, these results indicate the clinical value of arterial and venous whole blood measurements in perioperative management of sheep and can provide a reference for clinicians managing sheep after significant cardiovascular procedures.
Leishmaniasis, a disease of global relevance, results from infection with the protozoan parasite, Leishmania, which is transmitted to susceptible hosts through the bite of sand flies. Multiple forms of leishmaniasis may occur, including cutaneous, mucocutaneous, and visceral. Research with animal models remains an important approach to help define basic pathophysi- ologic processes associated with infection and disease. In this regard, mice and hamsters represent the most commonly used models. The severity of leishmaniasis in animal models depends on several factors, including genotype of the host and parasite and the dose and route of administration of the parasite to the host, and severity of outcome may range from subclinical to severe illness. This review provides basic background on leishmaniasis, relevant animal models, the pathophysiology and clinical signs in animals used as models of leishmaniasis, and general approaches to mitigate risk to personnel.
Murine fur mites are commonly excluded in modern research animal programs, yet infestations continue to persist due to challenges in detection and control. Because all diagnostic methods and treatment options have limitations, programs must make many operational decisions when trying to eradicate these ectoparasites. The primary aim of this study was to assess various durations of treatment time with an ivermectin-compounded diet in eliminating Radfordia affinis in mice as determined by PCR testing and pelt examination. A shorter treatment duration would be highly advantageous as compared with the current regimen of 8 wk as it would minimize cost and time for animal management programs, impediments to research, and ivermectin drug effects on infested animals. Five experimental groups of R. affinis-positive mice received dietary ivermectin for 0, 2, 4, 6, or 8 wk. A fur mite-negative, naïve mouse was added to each group every 8 wk to perpetuate the infestation and amplify any remaining populations of fur mites. At 16 wk after the respective treatment end, PCR testing was performed for all treated groups in conjunction with the positive control group (no treatment). Visual examination of pelts for mites and eggs via direct microscopy was also performed at each time point. All treated mice were free of R. affinis at 16 wk after the end of treatment as confirmed by both PCR testing and pelt examination. These findings indicate that a dietary ivermectin treatment duration of as little as 2 wk is effective in eliminating R. affinis, making successful eradication initiatives more achievable.
The zebra finch (Taeniopygia castanotis) is a songbird sold in the pet trade and commonly used in research. In this report, we describe a set of partially overlapping traits shared by 3 birds in 2 broods from the same nest box that included atypical morphologic, developmental, and behavioral characteristics. The most obvious feature of this novel phenotype was feathers exhibiting a clumped appearance, which was accompanied by slow growth, delayed expression of adult plumage traits, and tameness, which we define as a lack of escape response upon handling without behavioral indicators of stress such as rapid breathing. Surprisingly, these birds also displayed a fatal response to nonhuman stressors. In one brood, a male expressed all of these characteristics, 2 females were wild-type, and a male sibling expressed only a hyperactive stress response but was otherwise normal. This indicates that the stress response could be inherited independently of the other abnormalities found in the male nest mate. In a second brood, a male bearing the abnormal feather phenotype behaved similarly to the male in the first brood, supporting the possibility that tameness is genetically associated with the unusual feather phenotype. The 2 other male and 2 female nest mates from this brood were behaviorally and visually normal, although the females developed slowly. Although similar traits have appeared in the aviary previously, such as slow development and small size, these are the first cases documented in detail. This correlated suite of traits suggests a linkage among altered feather growth, developmental rate, and brain and/or physiologic traits influencing normal fear and stress responses in the zebra finch. Awareness and study of the mechanism(s) linking these traits by examination of underlying genetic or environmental factors will allow a better understanding of the relationship between physical and behavioral traits in domesticated laboratory animals.
Disturbances in gut microbiota are prevalent in inflammatory bowel disease (IBD), which includes ulcerative colitis (UC). However, whether these disturbances contribute to development of the disease or are a result of the disease is unclear. In pairs of human twins discordant for IBD, the healthy twin has a higher risk of developing IBD and a gut microbiota that is more similar to that of IBD patients as compared with healthy individuals. Furthermore, appropriate medical treatment may mitigate these disturbances. To study the correlation between microbiota and IBD, we transferred stool samples from a discordant human twin pair: one twin being healthy and the other receiving treatment for UC. The stool samples were transferred from the disease-discordant twins to germ-free pregnant dams. Colitis was induced in the offspring using dextran sodium sulfate. As compared with offspring born to mice dams inoculated with stool from the healthy cotwin, offspring born to dams inoculated with stool from the UC-afflicted twin had a lower disease activity index, less gut inflammation, and a microbiota characterized by higher α diversity and a more antiinflammatory profile that included the presence and higher abundance of antiinflammatory species such as Akkermansia spp., Bacteroides spp., and Parabacteroides spp. These findings suggest that the microbiota from the healthy twin may have had greater inflammatory properties than did that of the twin undergoing UC treatment.
Left ventricular noncompaction (LVNC) involving genetic mutation is categorized as an unclassified cardiomyopathy, and its diagnostic criteria have not been standardized. This could be because precise animal models of LVNC have not been created in any laboratory animal species. This study aimed to analyze the pathophysiology and familial tendency of LVNC in Japanese macaques. Two Japanese macaques with LVNC, and their parents who were suspected of having cardiac disease, were examined. One macaque with LVNC was examined using chest radiography, echocardiography, cardiac biomarkers, cardiac MRI, and pathologic examination, and the other macaque was examined using chest radiography, echocardiography, and cardiac biomarkers. Their common father and the mother of one of the macaques with LVNC were tested for chest radiography and cardiac biomarkers. Echocardiography revealed a meshwork with trabeculation and deep intertrabecular recesses in all their left ventricular walls. The 2 macaques with LVNC demonstrated a layered appearance of the myocardium, consisting of noncompacted myocardium on the endocardial side and compacted myocardium on the epicardial side, with a noncompacted/compacted ratio of 6.0 and 5.8, respectively. One of the 2 macaques with LVNC (case 1) had elevated levels of troponin I, troponin T, atrial natriuretic peptide, and brain natriuretic peptide. The second macaque with LVNC (case 2) showed blood flow in the intertrabecular recesses on echocardiography. The common father (case 3) of the 2 macaques with LVNC and the mother (case 4) of one of the macaques with LVNC had elevated levels of troponin I and troponin T. In case 1, histopathologic examination revealed fibrous thickening of the endocardium, fibrosis of the myocardial interstitium, myocardial disarray, vacuolar degeneration, anisonucleosis, and necrosis of myocardial cells. This suggests that Japanese macaques could serve as a reliable animal model of human LVNC.
The globally important human diseases of trench fever, epidemic typhus, and relapsing fever are vectored by the human louse Pediculus humanus humanus. Although these conditions are epidemically quiescent at present, they persist in socially dysfunctional situations of war, deprivation, and crowding. The taxonomically closely related head louse, Pediculus humanus capitis, does not respect economic or social status and is quite common in most countries. The 2 types of lice are now recognized as conspecific ecotypes of a single species. While the body louse has been adapted for propagation in the laboratory by feeding in vivo on live rabbits, a similar animal model has not been developed for the host-specific head louse. Accordingly, research for treatment and control of the head louse has largely been performed by using laboratory-reared body lice. This review describes methods for the propagation of body lice in the laboratory and outlines at least 4 areas of research that require sufficient numbers of aged body louse cohorts produced in rabbits for use in controlled studies: 1) pediculicide development and resistance, 2) immunity and vaccine potential, 3) endosymbiotic bacteria needed by lice for nutrition, and 4) lice as vectors of human disease. The review concludes with a discussion of several ethical issues involved with the standard method of using unsedated rabbits and recommends consideration of providing sedating anesthetics for rabbits used in louse feeding procedures.
Human infection with dengue virus (DENV) results in significant morbidity and mortality around the world. Current methods to investigate virus-associated changes in insect feeding behaviors are largely restricted to video analysis of feeding events outside of the host or intravital microscopy. Electropenetrography, a method originally developed for plant-feeding insects, offers a promising alternative by allowing high-resolution recording of voltage changes across the insect bite interface. We compared recordings from DENV-infected Aedes aegypti mosquitoes feeding on uninfected mice and uninfected A. aegypti feeding on DENV-infected mice to controls of uninfected A. aegypti feeding on uninfected mice. We found significant mosquito behavioral changes in both DENV-infected groups compared with controls including longer feeding times and longer preingestion probing events for A. aegypti feeding on DENV-infected mice and a higher number of sequential probing events in DENV-infected A. aegypti feeding on uninfected mice. By recording mosquito feeding and probing events beneath the surface of the skin, we have been able to both confirm and add new dimensions to previous findings regarding DENV-associated behavior changes in A. aegypti. This provides a foundation for increasingly in-depth studies focusing on the transmission of the DENV between vectors and hosts.
Guanfacine, an α 2 adrenoceptor agonist, has been used to successfully treat self-injurious behavior in nonhuman primates, including macaques ( Macaca mulatta ) and baboons ( Papio anubis ). It does so by facilitating a correction to the dopaminergic system that mediates a reduction in impulsivity and reactivity. Given this, we assessed the potential efficacy of guanfacine to treat socially directed agonistic behavior in primates with an apparent reactive behavioral phenotype. We present data from 2 pigtail macaques ( Macaca nemestrina ): an intact adult male housed in a breeding group, and an experimentally naive adult female living in a research setting with her social partner. Baseline behavioral assessments suggested that both macaques showed extreme responses to external stressors that triggered them to aggress social partners often leading to wounding that required veterinary intervention. Both animals were tracked during the course of 1 y. Once treated regularly with guanfacine, both animals showed significant reduction in their agonistic behavior and the rate at which they wounded other animals. Indeed, in the year since the female has been treated with guanfacine she has never wounded her cagemate. By collecting regular and detailed behavioral observations on the male in the breeding colony, we were able to identify triggers for his aggression and to track the behavioral changes evidenced after guanfacine treatment. These data supported our hypothesis that his aggression reflected extreme reactivity to external stressors, rather than general anxiety. Importantly, we saw only a limited and short-lived reduction in the male's affiliative behavioral rates, and thus guanfacine had no sedative effect, but did successfully reduce his reactivity and resultant agonism and wounding.
Chlamydia muridarum (Cm) has reemerged as a moderately prevalent infectious agent in research mouse colonies. Despite its experimental use, few studies evaluate Cm’s effects on immunocompetent mice following its natural route of infection. A Cm field isolate was administered (orogastric gavage) to 8-wk-old female BALB/cJ (C) mice. After shedding was confirmed (through 95 d), these mice were cohoused with naïve C57BL/6J (B6), C, and Swiss (J:ARC[S]) mice (n = 28/strain) for 30 d. Cohoused mice (n = 3 to 6 exposed and 1 to 6 control/strain) were evaluated 7, 14, 21, 63, 120, and 180 d post-cohousing (DPC) via hemograms, serum biochemistry analysis, fecal quantitative PCR, histopathology, and Cm major outer membrane protein immunohistochemistry. Immunophenotyping was performed on spleen (B6, C, and S; n = 6/strain) and intestines (B6; n = 6) at 14 and 63 DPC. Serum cytokine concentrations were measured (B6; n = 6 exposed and 2 control) at 14 and 63 DPC. All B6 mice were shedding Cm by 3 through 180 DPI. One of 3 C and 1 of 6 S mice began shedding Cm at 3 and 14 DPC, respectively, with the remaining shedding thereafter. Clinical pathology was nonremarkable. Minimal-to-moderate enterotyphlocolitis and gastrointestinal-associated lymphoid tissue (GALT) hyperplasia were observed in 15 and 47 of 76 Cm-infected mice, respectively. Cm antigen was frequently detected in GALT-associated surface intestinal epithelial cells. Splenic immunophenotyping revealed increased monocytes and shifts in T-cell population subsets in all strains/time points. Gastrointestinal immunophenotyping (B6) revealed sustained increases in total inflammatory cells and elevated cytokine expression in innate lymphoid and effector T cells (large intestine). Elevated concentrations of proinflammatory cytokines were detected in the serum (B6). Results demonstrate that while clinical disease was not appreciated, 3 commonly used strains of mice are susceptible to chronic enteric Cm infection which may alter various immune responses. Considering the widespread use of mice to model gastrointestinal disease, institutions should consider excluding Cm from their colonies.
