Seoul Virus Infection and Spread in United States Home-Based Ratteries: Rat and Human Testing Results From a Multistate Outbreak Investigation.

BACKGROUND: During 2017, a multistate outbreak investigation occurred after the confirmation of Seoul virus (SEOV) infections in people and pet rats. A total of 147 humans and 897 rats were tested. METHODS: In addition to immunoglobulin (Ig)G and IgM serology and traditional reverse-transcription polymerase chain reaction (RT-PCR), novel quantitative RT-PCR primers/probe were developed, and whole genome sequencing was performed. RESULTS: Seventeen people had SEOV IgM, indicating recent infection; 7 reported symptoms and 3 were hospitalized. All patients recovered. Thirty-one facilities in 11 US states had SEOV infection, and among those with ≥10 rats tested, rat IgG prevalence ranged 2%-70% and SEOV RT-PCR positivity ranged 0%-70%. Human laboratory-confirmed cases were significantly associated with rat IgG positivity and RT-PCR positivity (P = .03 and P = .006, respectively). Genomic sequencing identified >99.5% homology between SEOV sequences in this outbreak, and these were >99% identical to SEOV associated with previous pet rat infections in England, the Netherlands, and France. Frequent trade of rats between home-based ratteries contributed to transmission of SEOV between facilities. CONCLUSIONS: Pet rat owners, breeders, and the healthcare and public health community should be aware and take steps to prevent SEOV transmission in pet rats and to humans. Biosecurity measures and diagnostic testing can prevent further infections.

Evaluation of serological testing for Lyme disease in Military Health System beneficiaries in Germany, 2013-2017.

Lyme disease diagnostic workups conducted on active and retired U.S. service members and their dependents at U.S. Air Force military treatment facilities (MTFs) in Germany between 2013 and 2017 were assessed to determine the appropriateness of laboratory testing and antibiotic prescriptions. Of the 1,176 first-tier immunoassays, 1,114 (94.7%) were negative, and of the 285 immunoglobulin M (IgM) immunoblots, 242 (84.9%) followed a negative first-tier assay or were performed without an antecedent first-tier assay. Eighty-three positive IgM immunoblot tests were adjudicated using modified published criteria, of which 40 (48.2%) were deemed false positives. Thirtytwo patients with false-positive tests were treated with an antibiotic. Additionally, 30 patients with uncomplicated erythema migrans could have been treated without laboratory confirmation. Understanding the use and limitations of 2-tier diagnostic criteria, as well as the common pitfalls in diagnosing Lyme disease, may help prevent overdiagnosis, reduce unnecessary testing, and promote antibiotic stewardship.

New National Record for Culex perexiguus from Kuwait.

Mosquitoes can transmit a wide variety of viral and parasitic pathogens. Several species have recently been reported in new locations throughout the Arabian Peninsula as a result of entomological surveillance by the US military. We report a new national record for Culex perexiguus from Kuwait based on morphologic and molecular identification of captured samples. This mosquito might pose a public health threat to local populations and to military personnel as a potential vector of both Sindbis and West Nile viruses.

Notes from the Field: Increase in Human Cases of Tularemia--Colorado, Nebraska, South Dakota, and Wyoming, January-September 2015.

Tularemia is a rare, often serious disease caused by a gram-negative coccobacillus, Francisella tularensis, which infects humans and animals in the Northern Hemisphere. Approximately 125 cases have been reported annually in the United States during the last two decades. As of September 30, a total of 100 tularemia cases were reported in 2015 among residents of Colorado (n = 43), Nebraska (n = 21), South Dakota (n = 20), and Wyoming (n = 16) (Figure). This represents a substantial increase in the annual mean number of four (975% increase), seven (200%), seven (186%) and two (70%) cases, respectively, reported in each state during 2004-2014.

Human Plague - United States, 2015.

Since April 1, 2015, a total of 11 cases of human plague have been reported in residents of six states: Arizona (two), California (one), Colorado (four), Georgia (one), New Mexico (two), and Oregon (one). The two cases in Georgia and California residents have been linked to exposures at or near Yosemite National Park in the southern Sierra Nevada Mountains of California. Nine of the 11 patients were male; median age was 52 years (range = 14-79 years). Three patients aged 16, 52, and 79 years died.

Outbreak of Human Pneumonic Plague with Dog-to-Human and Possible Human-to-Human Transmission--Colorado, June-July 2014.

On July 8, 2014, the Colorado Department of Public Health and Environment (CDPHE) laboratory identified Yersinia pestis, the bacterium that causes plague, in a blood specimen collected from a man (patient A) hospitalized with pneumonia. The organism had been previously misidentified as Pseudomonas luteola by an automated system in the hospital laboratory. An investigation led by Tri-County Health Department (TCHD) revealed that patient A's dog had died recently with hemoptysis. Three other persons who had contact with the dog, one of whom also had contact with patient A, were ill with fever and respiratory symptoms, including two with radiographic evidence of pneumonia. Specimens from the dog and all three human contacts yielded evidence of acute Y. pestis infection. One of the pneumonia cases might have resulted through human-to-human transmission from patient A, which would be the first such event reported in the United States since 1924. This outbreak highlights 1) the need to consider plague in the differential diagnosis of ill domestic animals, including dogs, in areas where plague is endemic; 2) the limitations of automated diagnostic systems for identifying rare bacteria such as Y. pestis; and 3) the potential for milder plague illness in patients taking antimicrobial agents. Hospital laboratorians should be aware of the limitations of automated identification systems, and clinicians should suspect plague in patients with clinically compatible symptoms from whom P. luteola is isolated.

Molecular detection and identification of Bartonella species in rat fleas from northeastern Thailand.

The presence of Bartonella species in Xenopsylla cheopis fleas collected from Rattus spp. (R. exulans, R. norvegicus, and R. rattus) in Khon Kaen Province, Thailand was investigated. One hundred ninety-three fleas obtained from 62 rats, were screened by polymerase chain reaction using primers specific for the 16S-23S intergenic spacer region, and the presence of Bartonella DNA was confirmed by using the citrate synthase gene. Bartonella DNA was detected in 59.1% (114 of 193) of fleas examined. Sequencing demonstrated the presence of Bartonella spp. similar to B. elizabethae, B. rattimassiliensis, B. rochalimae, and B. tribocorum in the samples tested with a cutoff for sequence similarity ≥ 96% and 4 clustered together with the closest match with B. grahamii (95.5% identity). If X. cheopis proves to be a competent vector of these species, our results suggest that humans and animals residing in this area may be at risk for infection by several zoonotic Bartonella species.

Ecology of potential West Nile virus vectors in Southeastern Louisiana: enzootic transmission in the relative absence of Culex quinquefasciatus.

A study of West Nile virus (WNV) ecology was conducted in St. Tammany Parish, Louisiana, from 2002 to 2004. Mosquitoes were collected weekly throughout the year using Centers for Disease Control and Prevention (CDC) light traps placed at 1.5 and 6 m above the ground and gravid traps. A total of 379,466 mosquitoes was collected. WNV was identified in 32 pools of mosquitoes comprising four species; 23 positive pools were from Culex nigripalpus collected during 2003. Significantly more positive pools were obtained from Cx. nigripalpus collected in traps placed at 6 m than 1.5 m that year, but abundance did not differ by trap height. In contrast, Cx. nigripalpus abundance was significantly greater in traps placed at 6 m in 2002 and 2004. Annual temporal variation in Cx. nigripalpus peak seasonal abundance has important implications for WNV transmission in Louisiana. One WNV-positive pool, from Cx. erraticus, was collected during the winter of 2004, showing year-round transmission. The potential roles of additional mosquito species in WNV transmission in southeastern Louisiana are discussed.

Experimental infection of three laboratory mouse stocks with a shrew origin Bartonella elizabethae strain: an evaluation of bacterial host switching potential.

BACKGROUND: Bartonella elizabethae has been reported as a causative agent of human illnesses and strains of this bacterium are commonly isolated from commensal small mammals in Asia. METHODS: Since the zoonotic potential of a pathogen is often related to its host switching ability, we explored the capacity of a B. elizabethae strain to host switch by subcutaneously inoculating groups of Swiss Webster, BALB/c, and C57BL/6 mice with the bacteria at a range of doses. RESULTS: A low number of mice in each of the three groups showed susceptibility to infection at high doses (10(5) and 10(6) bacteria), and developed bacteremias of 6-8 weeks duration. CONCLUSION: The capacity of this B. elizabethae strain to switch hosts can have important public health consequences for humans in areas of Asia where many small mammal populations have high bartonellae infection prevalences and live as commensals with humans.

Experimental infection of Swiss webster mice with four rat bartonella strains: host specificity, bacteremia kinetics, dose dependent response, and histopathology.

Groups of Swiss Webster outbred mice were each inoculated with one of four bartonella strains originally isolated from Rattus spp. at doses ranging from 10(1) to 10(7) bacteria per mouse. One strain, Rn1691yn (Bartonella coopersplainensis-like), infected mice and produced bacteremias at levels up to 10(5)bacteria/ml of blood and from 3 to 8 weeks duration. A dose dependent response was also observed with differing proportions of mice bacteremic following inoculation at different doses. In addition weeks-to-months long lags in bacteremia manifestation occurred following lower dose exposures. The possibility of bacterial transmission from bacteremic mice to uninfected cagemates was assessed and no naïve mice became infected from contacts with infected mice. Finally, a subset of bacteremic mice inoculated with high doses of Rn1691yn were examined histopathologically and multifocal, granulomatous lesions were detected in both liver and kidneys. The host specificity and infectivity of the strains is discussed in relation to their potential for zoonotic transmission to incidental hosts.

Human isolates of Bartonella tamiae induce pathology in experimentally inoculated immunocompetent mice.

BACKGROUND: Bartonella tamiae, a newly described bacterial species, was isolated from the blood of three hospitalized patients in Thailand. These patients presented with headache, myalgia, anemia, and mild liver function abnormalities. Since B. tamiae was presumed to be the cause of their illness, these isolates were inoculated into immunocompetent mice to determine their relative pathogenicity in inducing manifestations of disease and pathology similar to that observed in humans. METHODS: Three groups of four Swiss Webster female mice aged 15-18 months were each inoculated with 10(6-7) colony forming units of one of three B. tamiae isolates [Th239, Th307, and Th339]. A mouse from each experimental group was sampled at 3, 4, 5 and 6 weeks post-inoculation. Two saline inoculated age-matched controls were included in the study. Samples collected at necropsy were evaluated for the presence of B. tamiae DNA, and tissues were formalin-fixed, stained with hematoxylin and eosin, and examined for histopathology. RESULTS: Following inoculation with B. tamiae, mice developed ulcerative skin lesions and subcutaneous masses on the lateral thorax, as well as axillary and inguinal lymphadenopathy. B. tamiae DNA was found in subcutaneous masses, lymph node, and liver of inoculated mice. Histopathological changes were observed in tissues of inoculated mice, and severity of lesions correlated with the isolate inoculated, with the most severe pathology induced by B. tamiae Th239. Mice inoculated with Th239 and Th339 demonstrated myocarditis, lymphadenitis with associated vascular necrosis, and granulomatous hepatitis and nephritis with associated hepatocellular and renal necrosis. Mice inoculated with Th307 developed a deep dermatitis and granulomas within the kidneys. CONCLUSIONS: The three isolates of B. tamiae evaluated in this study induce disease in immunocompetent Swiss Webster mice up to 6 weeks after inoculation. The human patients from whom these isolates were obtained had clinical presentations consistent with the multi-organ pathology observed in mice in this study. This mouse model for B. tamiae induced disease not only strengthens the causal link between this pathogen and clinical illness in humans, but provides a model to further study the pathological processes induced by these bacteria.

Host-seeking heights, host-seeking activity patterns, and West Nile virus infection rates for members of the Culex pipiens complex at different habitat types within the hybrid zone, Shelby County, TN, 2002 (Diptera: Culicidae).

Host-seeking heights, host-seeking activity patterns, and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) infection rates were assessed for members of the Culex pipiens complex from July to December 2002, by using chicken-baited can traps (CT) at four ecologically different sites in Shelby County, TN. Host-seeking height was assessed by CT placed at elevations of 3.1, 4.6, and 7.6 m during one 24-h period per month. Host-seeking activity was assessed by paired CT placed at an elevation of 4.6 m. Can traps were sampled at one 10-h daytime interval and at seven 2-h intervals during the evening, night, and morning. Cx. pipiens complex mosquitoes accounted for 87.1% of collected mosquitoes. Culex (Melanoconion) erraticus (Dyar & Knab) accounted for 11.9% of specimens. The average number of Cx. pipiens complex mosquitoes collected per 24-h CT period from July to September was lowest at a rural middle income site (1.7), intermediate at an urban middle income site (11.3), and highest at an urban low income site (47.4). Can traps at the forested site failed to collect Cx. pipiens complex mosquitoes. From July to September at urban sites, Culex pipiens pipiens L. was the rarest of the three complex members accounting for 11.1-25.6% of specimens. At the rural site, Culex pipiens quinquefasciatus Say was the rarest member of the complex. Cx. p. pipiens was not collected after September. Mean abundance of Cx. pipiens complex mosquitoes was higher in traps at 7.6 m than in traps at 4.6 m. Abundances at 3.1 m were intermediate and not significantly different from abundances at the other heights. Initiation of host-seeking activity was associated with the end of civil twilight and activity occurred over an extended nighttime period lasting 8-10 h. All 11 WNV-positive mosquitoes were Cx. pipiens complex mosquitoes collected from urban sites in traps placed at elevations of 4.6 and 7.6 m. Infection rates were marginally nonsignificant by height. Infection rates, host-seeking heights, and activity patterns were not significantly different among members of the Cx. pipiens complex.

Oviposition activity patterns and West Nile virus infection rates for members of the Culex pipiens complex at different habitat types within the hybrid zone, Shelby County, TN, 2002 (Diptera: Culicidae).

Oviposition activity and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) infection rates were assessed for members of the Culex pipiens complex from July through December 2002 by using gravid traps placed at four ecologically different sites in the southern portion of the hybrid zone in Shelby County, TN. Molecular assays identified three members of the Cx. pipiens complex: Cx. pipiens pipiens L., Cx. p. quinquefasciatus Say, and Cx. p. pipiens-Cx. p. quinquefasciatus hybrids (hybrids). The Cx. pipiens complex accounted for 90% of mosquitoes collected in gravid traps. All 285 WNV-positive mosquitoes were Culex mosquitoes, and 277 (97%) were Cx. pipiens complex mosquitoes. Infection rates among members of the Cx. pipiens complex were not significantly different. Infection rates were significantly higher at two urban sites than at a rural site, and WNV was not detected at a forested site. At urban sites, abundances of members of the Cx. pipiens complex corresponded to a simple latitude model of the hybrid zone. Cx. p. quinquefasciatus was most abundant (46.4%), followed by hybrids (34.1%) and Cx. p. pipiens (19.5%). The relative abundances at a rural site were reversed with Cx. p. pipiens (48.4%) being most abundant. This demonstrates that spatial habitat variation may profoundly influence the distribution of members of the Cx. pipiens complex within the hybrid zone. Members of the Cx. pipiens complex did not display different oviposition patterns. However, oviposition patterns assessed hourly at urban and rural sites were significantly different. At urban sites, oviposition activity of Cx. pipiens complex mosquitoes was bimodal with an evening peak associated with sunset and a morning peak associated with sunrise. At the rural site, the evening peak was pronounced and the morning peak weak and similar to nighttime activity.

Quantification of West Nile virus in the saliva of Culex species collected from the southern United States.

Culex quinquefasciatus, Cx. restuans, Cx. pipiens complex, and Cx. nigripalpus were collected as larvae or egg rafts from the southern USA. Adult female mosquitoes were intrathoracically inoculated with approximately 1,000 plaque-forming units of West Nile virus (WNV) and saliva was collected from them 5 days later. The amount of infectious WNV in the saliva samples was quantified by plaque assay and WNV RNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR). More than 90% of the mosquitoes had either infectious virus or viral RNA in their saliva. The RT-PCR assay detected a greater percent of samples with WNV RNA than the plaque assay detected infectious virus. Pairwise comparisons revealed 6 significant differences between the 7 groups surveyed. The Cx. nigripalpus secreted lower mean amounts of WNV than 3 other groups, and a difference was found between early- and late-season Cx. quinquefasciatus collected in Louisiana.

West Nile virus-infected mosquitoes, Louisiana, 2002.

Human cases of West Nile virus (WNV) disease appeared in St. Tammany and Tangipahoa Parishes in southeastern Louisiana in June 2002. Cases peaked during July, then rapidly declined. We conducted mosquito collections from August 3 to August 15 at residences of patients with confirmed and suspected WNV disease to estimate species composition, relative abundance, and WNV infection rates. A total of 31,215 mosquitoes representing 25 species were collected by using primarily gravid traps and CO2-baited light traps. Mosquitoes containing WNV RNA were obtained from 5 of 11 confirmed case sites and from 1 of 3 sites with non-WNV disease. WNV RNA was detected in 9 mosquito pools, including 7 Culex quinquefasciatus, 1 Cx. salinarius, and 1 Coquillettidia perturbans. Mosquito infection rates among sites ranged from 0.8/1,000 to 10.9/1,000. Results suggest that Cx. quinquefasciatus was the primary epizootic/epidemic vector, with other species possibly playing a secondary role.

Quantification of West Nile virus in vector mosquito saliva.

Saliva was collected from 4 species of mosquitoes intrathoracically inoculated with West Nile virus (WNV). The amount of infectious virus in the saliva was quantified by plaque assay and the number of WNV genomic equivalents (GE) was measured by reverse transcriptase-polymerase chain reaction. Ochlerotatus triseriatus had the greatest mean amount of infectious virus per saliva collection, followed by Aedes albopictus, Culex pipiens, and Cx. quinquefasciatus. The mean GE/saliva collection was also greatest in Oc. triseriatus, followed by Cx. quinquefasciatus, Cx. pipiens, and Ae. albopictus. The variance of log GE/saliva collection for Ae. albopictus was significantly lower than the variance for the other 3 species. This study provides a basis for comparing this component of vector competence and for determining the amounts of virus inoculated into vertebrates in experimental host competence studies.