A correlation analysis of metacarpal & phalangeal injury pattern from improvised explosive devices amongst armed force personnel

Injuries to the hand during military combat operations, particularly from improvised explosive devices (IEDs) have a significant impact on form, function, mental health and future employment but remain underreported amidst the life and limb-threatening emergencies that garner more attention. An understanding the patterns of hand injuries encountered from IEDs is crucial to optimizing reconstruction and rehabilitation. The aim of this study was to re-evaluate hand injury sustained from IED in order to understand the clinical burden for reconstruction and direct the focus for future hand protection. We identified 484 hand injuries in 380 patients sustained as a result of IEDs among military personnel service in Afghanistan between 2006 and 2013. 53% of all surviving military personnel injured by IEDs sustain injuries to the hand. Analysis of the 103 patients who sustained injury to the metacarpal, phalanges or digital amputation revealed that the middle and ring fingers are most commonly injured. Amputation to the ring finger is strongly associated with injury to the adjacent fingers and amputations to the middle, ring and little fingers concurrently is a commonly observed pattern. The proximal phalanges of the middle and ring fingers had a strong correlation for fracture together. These findings disprove the conventional belief in an ulnar focus of injury and support the quest for a development of combat hand protection that addresses the injury pattern seen.

Meta-analysis of antibiotics for simple hand injuries requiring surgery

BACKGROUND

Simple hand trauma is very common, accounting for 1·8 million emergency department visits annually in the USA alone. Antibiotics are used widely as postinjury prophylaxis, but their efficacy is unclear. This meta-analysis assessed the effect of antibiotic prophylaxis versus placebo or no treatment on wound infection rates in hand injuries managed surgically.

METHODS

Embase, MEDLINE, PubMed, Cochrane Central, ClinicalTrials.gov and the World Health Organization International Clinical Trials Portal were searched for published and unpublished studies in any language from inception to September 2015. The primary outcome was the effect of antibiotic prophylaxis on wound infection rates. Open fractures, crush injuries and bite wounds were excluded. Study quality was assessed using the Cochrane risk-of-bias tool. Data were pooled using random-effects meta-analysis, and risk ratios (RRs) and 95 per cent c.i. obtained.

RESULTS

Thirteen studies (2578 patients) were included, comprising five double-blind randomized clinical trials, five prospective trials and three cohort studies. There was no significant difference in infection rate between the antibiotic and placebo/no antibiotic groups (RR 0·89, 95 per cent c.i. 0·65 to 1·23; P = 0·49). Subgroup analysis of the five double-blind randomized clinical trials (864 patients) again found no difference in infection rates (RR 0·66, 0·36 to 1·21; P = 0·18).

CONCLUSION

There was moderate-quality evidence that routine use of antibiotics does not reduce the infection rate in simple hand wounds that require surgery.

Necrotising soft tissue infection in a UK metropolitan population

INTRODUCTION

Necrotising soft tissue infection (NSTI) is a rare but life threatening diagnosis. Geographic, economic and social variances influence presentation and prognosis. As the current literature does not reflect a UK metropolitan population, we conducted a retrospective chart review to establish pertinent features relevant to our practice.

METHODS

Patients with histologically confirmed diagnoses of NSTI presenting to two London teaching hospitals between January 2007 and July 2013 were included in the study. Features of presentation, surgical and medical management, microbiological findings and outcome were evaluated.

RESULTS

Twenty-four patients with histologically confirmed NSTI were included. Two age clusters were identified, with means of 46 years (standard deviation [SD]: 10 years) and 80 years (SD: 6 years). Pain, erythema and sepsis were common findings. Hypertension, hypercholesterolaemia and type II diabetes mellitus were common co-morbidities. A third of younger patients had human immunodeficiency virus or hepatitis C, with a quarter dependent on drugs and/or alcohol. The mean Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC) score was 5.8 (SD: 3.3). The lower extremities, groin and perineum were common sites of infection. Fourteen patients required inotropic support and seventeen required transfusions. The median number of surgical procedures was 5 (range: 1-17). Group A Streptococcus was the most frequently identified pathogen. Five patients died. Being elderly, female sex and failure to use clindamycin as a first-line antibiotic were associated with significantly higher mortality.

CONCLUSIONS

In contrast to other recent series, group A streptococcal monomicrobial NSTI remains the most common presentation in our population. Survival is anticipated in young patients, regardless of premorbid status. Elderly patients have a poor prognosis. The negative predictive value of the LRINEC score is questioned. Use of clindamycin as a first-line antibiotic is supported.

Systematic review of molecular mechanism of action of negative-pressure wound therapy

BACKGROUND

Negative-pressure wound therapy (NPWT) promotes angiogenesis and granulation, in part by strain-induced production of growth factors and cytokines. As their expression profiles are being unravelled, it is pertinent to consider the mode of action of NPWT at the molecular level.

METHODS

MEDLINE (January 1997 to present), Embase (January 1997 to present), PubMed (no time limit), the Cochrane Database of Systematic Reviews and the Cochrane Controlled Trials Register were searched for articles that evaluated the influence of NPWT on growth factor expression quantitatively.

RESULTS

Sixteen studies met the inclusion criteria. Tumour necrosis factor expression was reduced in acute and chronic wounds, whereas expression of interleukin (IL) 1β was reduced in acute wounds only. Systemic IL-10 and local IL-8 expression were increased by NPWT. Expression of vascular endothelial growth factor, fibroblast growth factor 2, transforming growth factor β and platelet-derived growth factor was increased, consistent with mechanoreceptor and chemoreceptor transduction in response to stress and hypoxia. Matrix metalloproteinase-1, -2, -9 and -13 expression was reduced but there was no effect on their enzymatic inhibitor, tissue inhibitor of metalloproteinase 1.

CONCLUSION

Cytokine and growth factor expression profiles under NPWT suggest that promotion of wound healing occurs by modulation of cytokines to an anti-inflammatory profile, and mechanoreceptor and chemoreceptor-mediated cell signalling, culminating in angiogenesis, extracellular matrix remodelling and deposition of granulation tissue. This provides a molecular basis for understanding NPWT.

Pretibial lacerations: experience from a lower limb trauma centre and systematic review

BACKGROUND

Pretibial lacerations are an important and neglected problem among the elderly. Poor management leads to prolonged hospitalisation and terminal decline. This study summarises our experience and evidence from the literature to ascertain an evidence-based rationale for referral and management.

METHODS

Our data were obtained from review of a prospectively gathered database. Additionally, Pubmed, Embase, Medline, and the Cochrane Database of Systematic Reviews were searched through July 2013, with eligible studies evaluated using standard methodology.

RESULTS

Seventy-three pretibial lacerations in 73 patients (63 females) were identified. Mean age was 78 ± 14, 1SD. Sixty patients were managed operatively with a mean length of stay of 11 ± 7 days, 1SD when uncomplicated by medical co-morbidity. Seven deaths occurred (4 in-hospital; 2 treated surgically and 2 treated conservatively) and 3 deaths occurred within 3 months of discharge; a death rate more than twice that of matched controls. Donor site "over-grafting" was performed in 19 cases and resulted in accelerated donor site healing (11 ± 9 days, 1SD vs. 29 ± 42 days, 1SD; P < 0.001). Negative pressure wound therapy delayed discharge (21 ± 23 days, 1SD vs. 15 ± 14 days, 1SD; P = 0.028). Microbiological sampling is unhelpful. Bed rest is unnecessary. "De-fatting" the flap is unproven.

CONCLUSION

Admissions expose the elderly to physical/functional decline and death. Our findings support a change of practice, minimising admissions for minor (Dunkin type I/II) injuries and rapid, protocol-driven surgical intervention and discharge for Dunkin type III/IV injuries with avoidance of negative pressure wound therapy in all but selected cases.

Cochrane corner: bone morphogenetic protein (BMP) for fracture healing in adults

BACKGROUND

Delay in fracture healing is a complex clinical and economic issue for patients and health services.

OBJECTIVES

To assess the incremental effectiveness and costs of bone morphogenetic protein on fracture healing in fractures and nonunions compared with standards of care.

SEARCH STRATEGY

We searched The Cochrane Library (2008, Issue 4), MEDLINE, and other major health and health economics databases (to October 2008).

SELECTION CRITERIA

Randomized controlled trials (RCTs) and full or partial economic evaluations of bone morphogenetic protein for fracture healing in skeletally mature adults.

DATA COLLECTION AND ANALYSIS

All clinical and economic data were extracted by one author and checked by another.

Anticipating the species jump: surveillance for emerging viral threats

Zoonotic disease surveillance is typically triggered after animal pathogens have already infected humans. Are there ways to identify high‐risk viruses before they emerge in humans? If so, then how and where can identifications be made and by what methods? These were the fundamental questions driving a workshop to examine the future of predictive surveillance for viruses that might jump from animals to infect humans. Virologists, ecologists and computational biologists from academia, federal government and non‐governmental organizations discussed opportunities as well as obstacles to the prediction of species jumps using genetic and ecological data from viruses and their hosts, vectors and reservoirs. This workshop marked an important first step towards envisioning both scientific and organizational frameworks for this future capability. Canine parvoviruses as well as seasonal H3N2 and pandemic H1N1 influenza viruses are discussed as exemplars that suggest what to look for in anticipating species jumps. To answer the question of where to look, prospects for discovering emerging viruses among wildlife, bats, rodents, arthropod vectors and occupationally exposed humans are discussed. Finally, opportunities and obstacles are identified and accompanied by suggestions for how to look for species jumps. Taken together, these findings constitute the beginnings of a conceptual framework for achieving a virus surveillance capability that could predict future species jumps.

The microbiological basis for a revised antibiotic regimen in high-energy tibial fractures: preventing deep infections by nosocomial organisms

BACKGROUND

Deep surgical site infections (SSI's) complicate Gustilo IIIB tibial fractures in 8-13% of cases. Antibiotic prophylaxis typically covers environmental contaminants. However, nosocomial organisms are usually implicated in deep infection. We used the microbiological profile of infected Gustilo IIIB tibial fractures to define a new, dynamic prophylactic regimen which recognises the need for prophylaxis against nosocomial organisms at the time of definitive closure.

METHODS

The microbiological profiles of Gustilo IIIB tibial fractures presenting over a 2-year period from January 2006 to December 2007 were reviewed. The environmental contaminants were compared with the organisms isolated from deep SSI's and correlated with the prophylactic antibiotic regimen used.

RESULTS

Fifty-two patients were included. Nine developed a deep tissue infection. The pathogens implicated included resistant Enterococci, Pseudomonas, Enterobacter and MRSA. Standard antibiotic prophylaxis provided cover for these combinations in only one of nine cases. This would have improved to eight of nine cases with the use of teicoplanin and gentamicin, given as a one-time dose during definitive soft-tissue closure. Specimens taken from wound debridement were neither sensitive nor specific for the subsequent development of deep infection and did not predict the organisms responsible.

CONCLUSIONS

Following high-energy open fracture, a single prophylactic antibiotic regimen directed against environmental wound contaminants does not provide cover for the organisms responsible for deepest SSI's and may have depopulated the niche, promoting nosocomial contamination prior to definitive closure. We advocate a dynamic prophylactic strategy, tailoring a second wave of prophylaxis against nosocomial organisms at the time of definitive wound closure, and at the same time avoiding the potential complications of prolonged antibiotic use.

Commensal ecology, urban landscapes, and their influence on the genetic characteristics of city-dwelling Norway rats (Rattus norvegicus)

Movement of individuals promotes colonization of new areas, gene flow among local populations, and has implications for the spread of infectious agents and the control of pest species. Wild Norway rats (Rattus norvegicus) are common in highly urbanized areas but surprisingly little is known of their population structure. We sampled individuals from 11 locations within Baltimore, Maryland, to characterize the genetic structure and extent of gene flow between areas within the city. Clustering methods and a neighbour-joining tree based on pairwise genetic distances supported an east-west division in the inner city, and a third cluster comprised of historically more recent sites. Most individuals (approximately 95%) were assigned to their area of capture, indicating strong site fidelity. Moreover, the axial dispersal distance of rats (62 m) fell within typical alley length. Several rats were assigned to areas 2-11.5 km away, indicating some, albeit infrequent, long-distance movement within the city. Although individual movement appears to be limited (30-150 m), locations up to 1.7 km are comprised of relatives. Moderate F(ST), differentiation between identified clusters, and high allelic diversity indicate that regular gene flow, either via recruitment or migration, has prevented isolation. Therefore, ecology of commensal rodents in urban areas and life-history characteristics of Norway rats likely counteract many expected effects of isolation or founder events. An understanding of levels of connectivity of rat populations inhabiting urban areas provides information about the spatial scale at which populations of rats may spread disease, invade new areas, or be eradicated from an existing area without reinvasion.

Atrophy of the intrinsic musculature of the hands associated with the use of botulinum toxin-A injections for hyperhidrosis: a case report and review of the literature

Botulinum toxin type A (BTX-A) has been used therapeutically for the treatment of spastic disorders for many years. More recently, the therapeutic utility of BTX-A in the treatment of hyperhidrosis has been recognised. While studies have reported on the efficacy of BTX-A in managing hyperhidrosis, long term data are required in order for the treatment implications to be fully appreciated. We report on a case of severe atrophy of the intrinsic muscles of the hands in a patient treated with intra-palmar BTX-A (Dysport, Speywood, UK) injections for hyperhidrosis. To our knowledge this has not been described in the literature before.

A survey of rodent-borne pathogens carried by wild-caught Norway rats: A potential threat to laboratory rodent colonies

Summary

Unintentional infection of laboratory rodents can compromise scientific research as well as the health of the animals and animal handlers. The source of contamination often is unknown, but may be introduced by wild rats from surrounding environments. To determine whether rats in Baltimore, Maryland, USA carry infectious agents commonly found in laboratory rodent colonies, we live-trapped 162 rats during 2005 to 2006 and screened them for a panel of viruses, bacteria and parasites. Antibodies against rat coronavirus/sialodacryoadenitis virus (91.7%), Mycoplasma pulmonis (72.9%), cilia-associated respiratory bacillus (52.1%), rat parvovirus/rat minute virus (29.2%), Kilham rat virus (10.4%), Toolan's H-1 virus (10.4%), Sendai virus (4.2%) and Theiler's mouse encephalomyelitis virus (4.2%), were detected in wild-caught Norway rats. Antibodies against reovirus and pneumonia virus of mice were not detected in wild Norway rats. Endoparasites, including Nippostrongylus braziliensis (71.6%), Rodentolepis nana or Hymenolepis diminuta (34.4%), Hetarakis spumosa (24.1%) and Trichuris muris (14.8%), as well as ectoparasites (14.8%), were identified in wild-caught rats. The risk of pathogen transmission from wild-caught rats to laboratory colonies needs to be mitigated by minimizing exposures rather than assuming wild animals represent a minimal hazard.

Nasal tip necrosis--an unusual presentation of rheumatoid vasculitis

We describe an unusual case of cutaneous necrosis of the nasal tip presenting to a facial reconstructive surgeon. The patient had developed this painless necrosis over a period of about 10 days. Her past medical history included rheumatoid arthritis. She described an exacerbation of her arthritic symptoms in the weeks preceding the development of the nasal tip necrosis. Her rheumatoid arthritis had been managed with corticosteroid and immunosuppressive therapy for more than 3 years. She had not previously experienced extra-articular manifestations (EAMs). A biopsy was taken and histological analysis identified a lymphocytic vasculitis. She was referred to her rheumatologist, and surgical management of her necrotic nasal tip commenced.

A survey of zoonotic pathogens carried by Norway rats in Baltimore, Maryland, USA

Norway rats (Rattus norvegicus) carry several zoonotic pathogens and because rats and humans live in close proximity in urban environments, there exists potential for transmission. To identify zoonotic agents carried by rats in Baltimore, Maryland, USA, we live-trapped 201 rats during 2005-2006 and screened them for a panel of viruses, bacteria, and parasites. Antibodies against Seoul virus (57.7%), hepatitis E virus (HEV, 73.5%), Leptospira interrogans (65.3%), Bartonella elizabethae (34.1%), and Rickettsia typhi (7.0%) were detected in Norway rats. Endoparasites, including Calodium hepatica (87.9%) and Hymenolepis sp. (34.4%), and ectoparasites (13.9%, primarily Laelaps echidninus) also were present. The risk of human exposure to these pathogens is a significant public health concern. Because these pathogens cause non-specific and often self-limiting symptoms in humans, infection in human populations is probably underdiagnosed.

Modeling the spread of annual influenza epidemics in the U.S.: the potential role of air travel

The role of air travel in the global spread of influenza has been the subject of a significant body of research, but this question has yet to be explored within the U.S. The goal of this research is to explore whether knowledge of U.S. air travel patterns and volumes leads to better forecasting of epidemics. We report the results of a series of simulations for the 1998-1999 through 2000-2001 influenza seasons using a standard compartmental model coupled with air transportation data. These preliminary results suggest that air travel may play an important role in the spread of annual influenza within the U.S., particularly in cities with large air travel volumes.

Forecasting the geographical spread of smallpox cases by air travel

Instituting air travel restrictions to slow the geographical spread of smallpox cases would have significant consequences and present serious logistical concerns. Public health decision makers must weigh the potential benefits of such restrictions against their negative impact. The goal of this research is to provide a basic analytical framework to explore some of the issues surrounding the use of air travel restrictions as a part of an overall containment strategy. We report preliminary results of a compartmental model for the inter-city spread of smallpox cases resulting from US domestic air travel. Although air traffic can be halted within hours as was shown following the terrorist attacks of 11 September 2001, these results suggest that the consequences of halting domestic air travel may not be outweighed by public health benefits.

Sex differences in immune responses and viral shedding following Seoul virus infection in Norway rats

In the field, male rodents are more frequently infected with hantaviruses than females. This study examined whether patterns of immune responses against hantavirus differed between the sexes. Male and female Long Evans rats (Rattus norvegicus) were inoculated with Seoul virus, and antibody and cytokine responses, as well as virus shedding were assessed. Males were more likely to shed virus in saliva, to shed virus through multiple routes (saliva, urine, and feces), and to have viral RNA in the spleen than females. Anti-Seoul virus IgG responses were higher in males than females. In both sexes, splenic IFNgamma and IL-4 production increased following infection. After infection, males had higher Th1 immune responses (i.e., IgG2a, IFNgamma, and IL-2) than females; in contrast, Th2 immune responses (i.e., IgG1, IL-4, and IL-10) were similar between the sexes. These data suggest that immune responses to Seoul virus differ between the sexes.

Sex differences in Seoul virus infection are not related to adult sex steroid concentrations in Norway rats

Field studies of hantavirus infection in rodents report that a higher percentage of infected individuals are males than females. To determine whether males were more susceptible to hantavirus infection than females, adult male and female Long Evans rats (Rattus norvegicus) were inoculated with doses of Seoul virus ranging from 10(-4) to 10(6) PFU. The 50% infective doses (ID(50)) were not significantly different for male and female rats (10(0.05) and 10(0.8) PFU, respectively). To determine whether sex differences in response to infection were related to circulating sex steroid hormones, sex steroid concentrations were manipulated and antibody responses and virus shedding were assessed following inoculation with the ID(90). Regardless of hormone treatment, males had higher anti-Seoul virus immunoglobulin G (IgG) and IgG2a (i.e., Th1) responses than females and IgG1 (i.e., Th2) responses similar to those of females. Males also shed virus in saliva and feces longer than females. Manipulation of sex steroids in adulthood did not alter immune responses or virus shedding, suggesting that sex steroids may organize adult responses to hantavirus earlier during ontogeny.

Application of a geographic information system to the tracking and control of an outbreak of shigellosis

A personal computer-based commercial geographic information system (GIS) was applied to an outbreak of Shigella sonnei infection at Fort Bragg, North Carolina. We used a database consisting of demographic, temporal, and home-address information for all recognized cases of S. sonnei that occurred among health care beneficiaries from 23 May 1997 through 14 August 1997. We imported this database into the GIS, which contained a digitized basemap of the local community. Through simultaneous examination of temporal and spatial distribution of the 59 identified cases of S. sonnei, a focus of infection in a single housing area was identified. Targeted education among residents of the neighborhood in which there was intense transmission was associated with prompt extinction of the epidemic. A GIS offers an efficient and practical way to directly visualize the dynamics of transmission of infectious diseases in the setting of a community outbreak.

Outbreak of hantavirus infection in the Four Corners region of the United States in the wake of the 1997-1998 El Nino-southern oscillation

Hantavirus cardiopulmonary syndrome (HCPS), a rodent-borne zoonosis, has been endemic in the Americas for at least several decades. It is hypothesized that the 1991-1992 El Niño-southern oscillation (ENSO) caused increased precipitation that allowed an increase in rodent population densities, thereby increasing the possibility of transmission to humans. The result was a 1993-1994 outbreak of the disease in the Four Corners states of the southwestern United States. A second strong ENSO occurred in 1997-1998, after a period of considerable public education about the risks of hantavirus infection that began during the 1993-1994 outbreak. The caseload of HCPS increased 5-fold above baseline in the Four Corners states in 1998-1999. Regions that had received increased rainfall in 1998 were especially affected. A large majority of the 1998-1999 case patients reported indoor exposure to deer mice. Hantavirus outbreaks can occur in response to abiotic events, even in the face of extensive public education and awareness.

Isolation of lactate dehydrogenase-elevating viruses from wild house mice and their biological and molecular characterization

Lactate dehydrogenase-elevating virus (LDV) was first identified as a contaminant of transplantable mouse tumors that were passaged in laboratory mice. It has been assumed that these LDVs originated from LDVs endemic in wild house mouse populations. In order to test this hypothesis and to explore the relationships between LDVs from wild house mice among each other and to those isolated from laboratory mice, we have isolated LDVs from wild house mice and determined their biological and molecular properties. We have screened for LDV tissues of 243 wild house mice that had been caught in various regions of North, Central and South America between 1985 and 1994. We were able to isolate LDVs from the tissues of four mice, three had been caught in Baltimore, MD and one in Montana. We demonstrate that the phenotypic properties (ability to establish a long-term viremic infection, low immunogenicity of the neutralization epitope, high resistance to antibody neutralization and lack of neuropathogenicity) of the four wild house mouse LDVs are identical to those of the primary LDVs isolated from transplantable tumors (LDV-P and LDV-vx), which are distinct from those of the neuropathogenic LDV-C. Furthermore, ORF 5 and ORF 2 and their protein products (the primary envelope glycoprotein VP-3P, and the minor envelope glycoprotein, respectively) of the wild house mouse LDVs were found to be closely related to those of LDV-P and LDV-vx. The LDVs caught in Baltimore, MD were especially closely related to each other, whereas the LDV isolated in Montana was more distantly related, indicating that it had evolved independently. The ectodomain of VP-3P of all four wild house mouse LDVs, like those of LDV-P and LDV-vx, possess the same three polylactosaminoglycan chains, two of which are lacking in the VP-3P ectodomain of LDV-C. These results further strengthen the conclusion that the three polylactosaminoglycan chains are the primary determinants of the phenotypic properties of LDV-P/vx.

Using remotely sensed data to identify areas at risk for hantavirus pulmonary syndrome

The 1993 U.S. hantavirus pulmonary syndrome (HPS) outbreak was attributed to environmental conditions and increased rodent populations caused by unusual weather in 1991- 92. In a case-control study to test this hypothesis, we estimated precipitation at 28 HPS and 170 control sites during the springs of 1992 and 1993 and compared it with precipitation during the previous 6 years by using rainfall patterns at 196 weather stations. We also used elevation data and Landsat Thematic Mapper satellite imagery collected the year before the outbreak to estimate HPS risk by logistic regression analysis. Rainfall at case sites was not higher during 1992-93 than in previous years. However, elevation, as well as satellite data, showed association between environmental conditions and HPS risk the following year. Repeated analysis using satellite imagery from 1995 showed substantial decrease in medium- to high-risk areas. Only one case of HPS was identified in 1996.

Population dynamics of a naturally occurring heterogeneous mixture of Borrelia burgdorferi clones

Two unique isolates of Borrelia burgdorferi, differing in plasmid content and outer surface protein C expression, were cultured on sequential captures of a single free-living Peromyscus leucopus mouse and were examined for differences in transmissibility. Both isolates were transmissible from inoculated C.B-17 mice to larval Ixodes scapularis ticks and, subsequently, from infected nymphal ticks to C3H/HeJ mice. Plasmid and protein analyses suggested that the original isolates were a mixed population of B. burgdorferi, and cloning by limiting dilution resulted in the identification of two clonal groups. In addition to being heterogeneous in plasmid and genomic macrorestriction analyses, the clones varied with respect to the electrophoretic mobilities and antigenicity of their OspC proteins, as shown by their reactivity to a panel of monoclonal antibodies. Plasmid analysis of sequential isolates from C3H mice experimentally infected with the primary isolate or various mixtures of its subclones showed an apparently random fluctuation in clonal dominance in the majority of mice. Surprisingly, mice infected with each subclone were permissive to superinfection with the heterologous subclone, despite the presence of anti-B. burgdorferi antibodies at the time of the secondary challenge. These results show conclusively that mice captured at Lyme disease enzootic sites may be infected by mixed populations of genetically and antigenically distinct B. burgdorferi clones and that these infections can be acquired by coinfection or by sequential infection. The lack of cross-immunization between clones existing within a naturally occurring population may play a role in the maintenance of the genetic heterogeneity of B. burgdorferi in nature.

Evidence for widespread infection of wild rats with hepatitis E virus in the United States

Hepatitis E is an important medical pathogen in many developing countries but is rarely reported from the United States, although antibody to hepatitis E virus (anti-HEV) is found in > 1% of U.S. citizens. Zoonotic spread of the virus is suspected. Sera obtained from 239 wild rats trapped in widely separated regions of the United States were tested for anti-HEV. Seventy-seven percent of rats from Maryland, 90% from Hawaii, and 44% from Louisiana were seropositive for anti-HEV. Rats from urban as well as rural areas were seropositive and the prevalence of anti-HEV IgG increased in parallel with the estimated age of the rats, leading to speculation that they might be involved in the puzzling high prevalence of anti-HEV among some U.S. city dwellers. The discovery of a in rats in the United States and the recently reported discovery that HEV is endemic in U.S. swine raise many questions about transmission, reservoirs, and strains of HEV in developed countries.

Vector-related case-control study of severe malaria in Kilifi District, Kenya

A case-control study examined vector-related and environmental parameters associated with severe malaria in Kilifi District along the coast of Kenya. Over an 11-month period, 119 children identified with severe malaria infections at the Kilifi District Hospital were matched by age with control children who reported to the outpatient clinic with nonsevere infections. Intensive mosquito sampling was done in each of the case-control houses over a four-day period, beginning within a week of index case admission. A total of 109 environmental, demographic, behavioral, and animal husbandry variables were characterized for each household. Vector species (Anopheles gambiae s.l. and An. funestus) were detected in 40.1% and 36.1% of case and control houses, respectively. The relative abundance of vectors in individual houses was stable over the two-week resampling periods (r = 0.9). Both the overall abundance of anopheline mosquitoes (odds ratio [OR] = 1.5) and P. falciparum sporozoite rates (OR = 1.5) were not significantly different between case and control houses. In a matched analysis, 11 of 109 house variables associated significantly with severe malaria were also associated with vector abundance, as determined by chi-square linear trend analysis. Under conditions of year-round, low-level transmission on the coast of Kenya, the risk of severe disease in children is multifactorial and not governed strictly by transmission intensity or environmental heterogeneity affecting vector abundance and distributions. This suggests that current interventions that appear to be achievable only in areas where transmission is already low to moderate should be appropriate. However, such interventions should be monitored so that inappropriate and possibly disastrous control activities can be avoided in Africa.

Antibody levels to recombinant tick calreticulin increase in humans after exposure to Ixodes scapularis (Say) and are correlated with tick engorgement indices

The antibody responses of subjects who presented with a definite Ixodes scapularis (Say) tick bite were measured to determine the utility of the antibody response against recombinant tick calreticulin (rTC) as a biologic marker of tick exposure. Subjects bitten by I. scapularis evidenced an increase in anti-rTC antibody levels between visit 1 and visit 2 from 24.3 to 27.1 ng/microl serum (n = 88, p = 0.003), and levels remained elevated at visit 3 (p = 0.005). These anti-rTC antibody levels during visits 2 and 3 were significantly higher than those in four non-exposed controls. Tick engorgement indices, measured on the biting ticks, were found to be correlated with anti-rTC antibody levels (e.g., for visit 3: Pearson's r = 0.357, p = 0.001). Tick engorgement index (TEI), ratio of body length to scutal width, was identified to be the only independent predictor of anti-rTC antibody levels in linear regression models. Logistic regression revealed that a bite from an I. scapularis tick that became engorged (TEI >3.4) was a risk factor for anti-rTC antibody seropositivity (adjusted odds ratio for age and bite location = 7.4 (95% confidence interval 2.1-26.4)). The anti-rTC antibody test had a sensitivity of 0.50 and a specificity of 0.86 for a bite from I. scapularis that became engorged. Immunoblotting revealed that subjects made a specific anti-rTC antibody response.

Longitudinal study of infection with Borrelia burgdorferi in a population of Peromyscus leucopus at a Lyme disease-enzootic site in Maryland

The maintenance of Borrelia burgdorferi in a population of Peromyscus leucopus was investigated from 202 mark and recapture mice and 61 mice that were removed from a site in Baltimore County, Maryland. Borrelia burgdorferi infection was detected by culture and polymerase chain reaction (PCR) of ear tissue, and exposure to the spirochete was quantified by serology. Overall prevalence of B. burgdorferi, as determined by culture and PCR of ear tissue at first capture, was 25% in the longitudinal sample and 42% in the cross-sectional sample. Significantly more juvenile mice were captured in the longitudinal sample (18%) than in the cross-sectional sample (0%). Among 36 captured juvenile mice, only one was infected with B. burgdorferi; this contributed to a significant trend for infection with B. burgdorferi with age. Recovery from infection with B. burgdorferi was not detected among 77 mice followed for an average of 160 days. The incidence rate of infection with B. burgdorferi was 10 times greater in mice captured during two periods of high risk of exposure to nymphal Ixodes scapularis ticks compared with a period of low risk. Maintenance of B. burgdorferi in this population was dependent on indirect transmission of the organism from infected ticks to susceptible mice and development of chronic infection with the spirochete, which had no measurable effect on the survival of infected mice.

Molecular and geographic patterns of tuberculosis transmission after 15 years of directly observed therapy

CONTEXT

Recent studies suggest that one third of tuberculosis cases in urban areas result from recent transmission. Improved tuberculosis control measures such as uniform implementation of directly observed therapy might reduce the proportion of cases resulting from recent transmission.

OBJECTIVE

To determine patterns of tuberculosis transmission in Baltimore, Md, after 15 years of community-based directly observed therapy.

DESIGN

A 30-month (January 1994-June 1996), prospective, city-wide study of all cases of tuberculosis using traditional contact investigations, geographic information systems data, and molecular epidemiologic comparison of Mycobacterium tuberculosis isolates with 2 DNA probes.

PATIENTS

One hundred eighty-two patients with culture-positive tuberculosis.

MAIN OUTCOME MEASURES

Proportion of disease defined as recently transmitted based on epidemiologic linkage by traditional contact tracing and molecular linkage by DNA fingerprint analysis of isolates; geographic foci of transmission based on linkage of residences by geographic information systems data.

RESULTS

Of the 182 patients who had isolates of M tuberculosis available, 84 (46%) showed molecular clustering with 58 (32%) defined as being recently transmitted. Only 20 (24%) of 84 cases with clustered DNA fingerprints had epidemiologic evidence of recent contact. Geographic analysis showed significant spatial aggregation of the 20 clustered cases with epidemiologic links (P<.001), occurring in areas of low socioeconomic status and high drug use. The 64 cases with clustered DNA fingerprints but without epidemiologic links shared common risk factors and demographic features with the 20 clustered patients who did have epidemiologic links.

CONCLUSIONS

Recently transmitted tuberculosis accounts for a high proportion of tuberculosis cases in Baltimore. Recently transmitted cases occur in geographically distinct areas of Baltimore, and location-based control efforts may be more effective than contact tracing for the early identification of cases.

Black Creek Canal Virus infection in Sigmodon hispidus in southern Florida

A total of 1,500 small mammals were collected and tested for antibodies cross-reactive to Sin Nombre virus (Hantavirus: Bunyaviridae) at 89 sites in a 1,600 km2 study area of southern Florida. More than 95% of the 123 seropositive animals were cotton rats (Sigmodon hispidus), suggesting infection by Black Creek Canal Virus, although seroreactive Rattus rattus (5 of 294) and Peromyscus gossypinus (1 of 39) also were captured. Crude seroprevalence in S. hispidus was 11%. Seroprevalence increased with body size and was more common in male (18%; n=451) than in female (6%; n=593) cotton rats. Infection within S. hispidus populations was widespread throughout the study area. Prevalence ranged from 0% to 60% at sites where more than five cotton rats were sampled but was not only a function of sample size. Sites with seropositive cotton rats were geographically clustered compared with sites with no seropositive cotton rats. Clustering was not due to the spatial distribution of sites with few animals, season of collection, or sex bias of animals captured at these sites. However, sites with no seropositive animals had an excess of animals in the intermediate size class (60-99 g) and a deficit of the largest and smallest animals. These data suggest that population structure within the habitat mosaic may play a significant role in the spatial distribution of hantavirus infection in local populations of reservoir species.

Kinetics and cross-species comparisons of host antibody responses to lone star ticks and American dog ticks (Acari: Ixodidae)

Understanding of the animal antibody response to tick salivary gland proteins is necessary to identify candidate antibodies that may have use as species- and feeding-duration-specific biomarkers of tick exposure in humans. The kinetics of the humoral immune response of rabbits to challenge feeding by 2 tick species [Amblyomma americanum (L.) and Dermacentor variabilis (Say)] was characterized by both enzyme-linked immunosorbent assay and immunoblot. Western blot analysis revealed that rabbits produced antibodies against both A. americanum and D. variabilis tick salivary gland antigens, with molecular weights ranging from 12.2 to 125 kDa; the antibody response against the saliva of both tick species possessed both unique and common aspects. The presence of antibody against low-molecular-mass (< 20 kDa) salivary gland antigens of A. americanum may be specific for A. americanum exposure. Antibodies directed against D. variabilis salivary gland antigens of 111, 86.3, and 85 kDa may be specific for D. variabilis exposure. The data suggest that host antibodies directed against specific tick salivary gland proteins might have use as species-specific biologic markers of tick exposure.

Antibody to a cDNA-derived calreticulin protein from Amblyomma americanum as a biomarker of tick exposure in humans

The antibody responses of human and animal hosts were studied to determine the utility of antibody against recombinant tick calreticulin (rTC), a cDNA-derived protein isolated from salivary glands of Amblyomma americanum L., as a biologic marker of tick exposure. Rabbits fed upon by either A. americanum or Dermacentor variabilis Say developed significant anti-rTC antibody responses, as measured by both ELISA and immunoblot assay. In contrast, gerbils exposed to Aedes aegypti did not develop anti-rTC antibodies, as measured by ELISA or immunoblot assay. The utility of the assay was next evaluated in humans at high risk for tick exposure. During April through September 1990, 192 military personnel who originated from either Fort Chaffee, Arkansas or Fort Wainwright, Alaska were studied during maneuvers in tick infested areas at Fort Chaffee. Study subjects completed a questionnaire and had pre- and post-maneuvers serum specimens analyzed for antibodies to rTC. In adjusted analysis (controlling for age, fort of origin, attached tick during maneuvers, and bed netting use), the use of bed netting and home station were associated with post-maneuvers anti-rTC antibody seropositivity by ELISA. Subjects from Fort Wainwright were more likely to be seropositive for anti-rTC antibody (adjusted odds ratio = 5.3, 95% confidence interval [CI] = 1.1-25.6). Personnel who did not report the use of bed netting were more likely to be anti-rTC seropositive (adjusted odds ratio = 6.8, 95% CI = 1.4-32.4). Immunoblot assays showed that humans had specific anti-rTC antibody responses. The animal experiments demonstrate that hosts exposed to naturally feeding ticks develop anti-rTC antibodies. The data also indicate that hosts exposed to Ae. aegypti saliva may not develop antibodies against rTC. Observations in tick-exposed humans support the hypothesis that anti-rTC antibody seropositivity is a biologic marker of tick exposure.

Epidemiology of rodent bites and prediction of rat infestation in New York City

The authors examined the epidemiology of rodent bites occurring in New York City from 1986 through 1994 to identify factors contributing to increased probability of rodent bite and rat infestation. City blocks on which a rodent bite case had been reported (n=415) and three control blocks per bite block, matched by borough and randomly selected, were compared according to demographic characteristics obtained from US Census data. Environmental variables were defined using a geographic information system to extract distances to areas potentially providing food or refuge for rats, such as parks. Borough-specific models of bite risk were generated by logistic regression using data collected from 1991 to 1994; risk values were then generated for all city blocks. Field surveys for signs of rat infestation conducted on 31 randomly selected blocks indicated a significant association between degree of infestation and predicted risk. Spatial analyses comparing neighboring blocks showed that blocks with bite cases were significantly clustered. The models based on data from previous years correctly predicted 72 percent of 53 block addresses of rodent bite cases from 1995 as being locations of high or intermediate risk. A combination of geographic and epidemiologic analyses could help investigators identify the spatial occurrence of rat infestation over a large area and might help to focus control activities.

Geographic epidemiology of gonorrhea in Baltimore, Maryland, using a geographic information system

The epidemiology of gonorrhea is characterized by geographically defined hyperendemic areas, or "cores." Geographic information system (GIS) technology offers new opportunities to evaluate these patterns. The authors developed a GIS system linked to the disease surveillance database at the Baltimore Health Department and used this system to evaluate the geographic epidemiology of gonorrhea in Baltimore, Maryland, during 1994. There were 7,330 reported cases, of which 87.4% were in persons aged 15-39 years; 56.6% were of the cases were in males; and 60.5% of the cases were reported from the nonsexually transmitted disease (STD) clinic sector. Valid residential addresses were available for 6,831 (93.5%) of cases. In the GIS system, gonorrhea cases were geocoded by reported address using digitized maps, and assigned to census tract. Census tract-specific rates for persons aged 15-39 years were calculated using 1990 census data. Gonorrhea was reported from 196/202 (97%) of census tracts, of which 90 census tracts had >30 cases. For these 90 census tracts, rates were ranked. The core was considered as the top rate quartile, consisting of 13 geographically contiguous census tracts with rates 4,370-6,370 per 100,000; adjacent areas were 19 census tracts in the second quartile (rates: 3,730-4,370 per 100,000). As radial distance from the core areas increased, incidence rates decreased and male/female ratio increased, which is consistent with previous definitions of the core theory of STD transmission. Mapping of cases by provider showed that cases reported from STD clinics had similar geographic distribution to those from the non-STD clinic sector. From an operational perspective, GIS can be effectively integrated with clinical data systems to provide epidemiologic analysis.

Using geographic information systems to assess spatial patterns of drug use, selection bias and attrition among a sample of injection drug users

This study sought to assess whether frequency and type of drug use are geographically located within the city of Baltimore independent of neighborhood characteristics. The second goal was to assess geographic factors associated with sample selection and attrition. The sample consisted of 597 inner-city injection drug users who were enrolled in a HIV prevention study. The residential locations were plotted using Geographic Information Systems (GIS) software. Three patterns of drug use in the prior 6 months were examined: daily use of injection heroin, daily use of injection cocaine and any use of crack cocaine. Daily use of cocaine and any use of crack were found to be statistically associated with residing in the western portion of the city and distance from the western district sexually transmitted disease clinic. After adjusting for individual level characteristics and neighborhood level variables, as measured by 1990 census tract data, daily use of cocaine was found to be associated with residing in a more southern area of the city and distance from the western district sexually transmitted disease clinic, and any crack use was found to be associated with residing in a more western area of the city and distance from the western district sexually transmitted disease clinic. Men and younger participants were more likely to reside further away from the study clinic as were individuals who dropped out of the intervention condition. The results of this study suggest that type and frequency of drug use is associated with specific geographic areas, independent of neighborhood characteristics. These results have implications for the location of drug prevention, needle exchange and other HIV prevention activities.

Retrospective serosurvey for human granulocytic ehrlichiosis agent in urban white-footed mice from Maryland

Archived serum samples from 111 Peromyscus leucopus, collected 1984-88 in Baltimore City (Maryland, USA), were analyzed by indirect immunofluorescence assay. Sera from two (2%) individuals contained antibodies reactive to Ehrlichia equi and the human granulocytic ehrlichiosis (HGE) agent. This suggests that the HGE agent or an antigenically related organism has been present in rodent populations in this locality for more than a decade, and was present in the region at least 12 yr before a case of human disease was recognized.

Experimental evaluation of rodent exclusion methods to reduce hantavirus transmission to humans in rural housing

An experimental assessment of methods to reduce rodent infestations in rural housing was conducted in Yosemite National Park, California, Sequoia/Kings Canyon National Parks, California, and Shenandoah National Park, Virginia. During pretreatment surveys, nearly all (63 of 68) selected units had past or ongoing rodent activity inside. Active infestations were found in 58.8% of the units. Peromyscus spp. represented 91.2% of all animals caught inside housing units. Despite little harborage, rodent activity was common near housing (290 animals/2,254 trap nights). The most common species present was Peromyscus maniculatus (43-50% of all captures). This species was especially frequent (49-87% of Peromyscus captures) around the foundations of housing units. Habitat had little effect on captures. There were 1.8 Peromyscus caught per unit along the foundations of housing in modified rural settings with grass lawns compared with 1.2 Peromyscus caught per unit in sites located in mature woodlands. During autumn of 1994, randomly selected housing units were rodent proofed by sealing openings associated with chases, roof eaves, and attics with insulation and wire mesh. Housing was examined and the fauna was resampled in the spring-summer of 1995. Rodent-proofed houses were infested significantly less often (3 of 28) than control houses (13 of 36) (P = 0.02) and the intensity of infestation was lower in experimental houses (6 versus 23 mice/treatment). More than 25% of the mice trapped inside the houses had been marked outside the houses during the three-day surveys, demonstrating movement of mice adjacent to the buildings into not rodent-proofed housing. As in the previous autumn, most of the animals captured in (98.9%) and along the foundations of the houses (77.5%) were Peromyscus spp. These results demonstrate that Peromyscus frequently invade rural housing but rodent-proofing effectively eliminates or substantially reduces rodent activity.

Sporadic urban leptospirosis

BACKGROUND

Surprisingly, many inner-city residents have antibodies to Leptospira interrogans. The manner in which these persons acquire this organism in the absence of recognized occupational, recreational, or epidemic risk factors is not known.

OBJECTIVE

To study the epidemiology of patients with leptospirosis who acquired L. interrogans in inner-city Baltimore, Maryland.

DESIGN

Epidemiologic investigation.

SETTING

Inner-city university hospital.

PATIENTS

Three inner-city residents who developed leptospirosis.

MEASUREMENTS

Trapping rats in alleys where the patients may have acquired L. interrogans; polymerase chain reaction (PCR) analysis of patients serum and cerebrospinal fluid specimens and rat tissues to determine the presence of leptospiral DNA; and serologic testing of serum from patients and rats by microagglutination assay to confirm L. interrogans infection.

RESULTS

Three patients developed leptospirosis after probable percutaneous exposure to rat (Rattus norvegicus) urine in Baltimore alleys. A PCR assay detected L. interrogans DNA in samples of body fluid obtained from the first two patients at presentation (one in cerebrospinal fluid, the other in serum). Results of PCR done on serum drawn from the third patient after antibiotic therapy began were negative. A microagglutination test showed that all patients had high levels of antibodies to the L. interrogans serogroup icterohaemorrhagiae. In 19 of 21 rats that were trapped in the alleys where the patients had sustained lacerations before illness developed, kidney or brain tissues were positive by PCR for the presence of L. interrogans.

CONCLUSIONS

A population was discovered to be at risk for acquiring L. interrogans: urban residents who are sporadically exposed to rat urine in the inner city. Inner-city rats often carry L. interrogans. Polymerase chain reaction can quickly establish the diagnosis of leptospirosis and is useful for epidemiologic study. An endemic substrate for the transmission of the organism is present in inner-city Baltimore. Leptospirosis may become increasingly recognized in deteriorating inner cities in which rat populations are expanding.

Salivary gland changes and host antibody responses associated with feeding of male lone star ticks (Acari:Ixodidae)

The goal of this study was to demonstrate that male lone star ticks, Amblyomma americanum (L.), actively feed on rabbits during attachment and that the host is capable of mounting an immune response against male salivary gland proteins. During attachment, it was shown that male ticks salivary glands hypertrophy. An enzyme-linked immunosorbent assay was used to detect rabbit serum proteins in the midgut of previously attached male ticks. SDS-polyacrylamide gel electrophoresis showed that the proteins expressed in the male tick salivary gland changed during feeding, with several new proteins in the 15- to 50-kDa range synthesized during attachment. Rabbits mounted a detectable antibody response against male tick salivary gland proteins after 2 sequential feedings of male ticks. The antibodies were directed against a spectrum of male salivary gland proteins ranging from 18 to 160 kDa. Several of these proteins were not recognized by antibodies directed against female tick saliva proteins, and thus may be specific male salivary gland components. This evidence indicates that male A. americanum ticks actively feed during attachment, that their salivary gland proteins change during feeding, and that male salivary gland proteins are immunogenic.

Acquired resistance and antibody response of raccoons (Procyon lotor) to sequential feedings of Ixodes scapularis (Acari: Ixodidae)

Captive-bred raccoons (Procyon lotor) developed immune resistance to infestation by the larval stage of the ixodid tick, Ixodes scapularis, the vector of Borrelia burgdorferi, following repeated applications of both nymphs and larvae. Resistance was expressed as a significant decrease in the proportion of engorged larvae recovered from each cohort. Resistance to nymphs was not noted, but, only two such cohorts were applied. Utilizing an enzyme-linked immunosor-bent assay (ELISA) developed to detect raccoon serum antibodies to tick salivary gland antigens, raccoons evidenced a two to ten-fold increase in anti-tick salivary extract antibody titer following the application of two cohorts of nymphs and eights cohorts of larvae. The tick saliva antigens recognized by both pre- and post-exposure raccoon sera were evaluated by Western blotting. The production of antibodies correlated with the development of resistance to infestation, suggesting that the resistance was immune-mediated and could be measured by anti-tick salivary extract antibody titers. Resistance in exposed raccoons prevents nearly 90% of larvae from prolonged feeding. Prolonged feeding is required for engorgement and the transmission of various infectious agents, such as B. burgdorferi.

Environmental risk factors for Lyme disease identified with geographic information systems

OBJECTIVES

A geographic information system was used to identify and locate residential environmental risk factors for Lyme disease.

METHODS

Data were obtained for 53 environmental variables at the residences of Lyme disease case patients in Baltimore County from 1989 through 1990 and compared with data for randomly selected addresses. A risk model was generated combining the geographic information system with logistic regression analysis. The model was validated by comparing the distribution of cases in 1991 with another group of randomly selected addresses.

RESULTS

In crude analyses, 11 environmental variables were associated with Lyme disease. In adjusted analyses, residence in forested areas (odds ratio [OR] = 3.7, 95% confidence interval [CI] = 1.2, 11.8), on specific soils (OR = 2.1, 95% CI = 1.0, 4.4), and in two regions of the county (OR = 3.5, 95% CI = 1.6, 7.4) (OR = 2.8, 95% CI = 1.0, 7.7) was associated with elevated risk of getting Lyme disease. Residence in highly developed regions was protective (OR = 0.3, 95% CI = 0.1, 1.0). The risk of Lyme disease in 1991 increased with risk categories defined from the 1989 through 1990 data.

CONCLUSIONS

Combining a geographic information system with epidemiologic methods can be used to rapidly identify risk factors of zoonotic disease over large areas.

Predicting Ixodes scapularis abundance on white-tailed deer using geographic information systems

We collected 1,410 Ixodes scapularis from 139 white-tailed deer in Kent County, Maryland during the 1990 hunting season. A geographic information system was used to extract 41 environmental variables in the areas surrounding the collection sites of the deer. Stepwise linear regression was used to evaluate the association between the abundance of ticks on deer and the environmental data. A significant statistical association was observed between the abundance of I. scapularis and seven environmental variables (R = 0.69). Tick abundance was negatively correlated with urban land use patterns, wetlands, the amount of privately owned land, soils that tended to be saturated with water, and one drainage system. Tick abundance was positively correlated with well-drained, sandy soils having low water tables. These results indicate that geographically referenced environmental data may be useful in anticipating the risk of exposure to vectors over large areas.