Nipah virus outbreak with person-to-person transmission in a district of Bangladesh, 2007.

In February 2007 an outbreak of Nipah virus (NiV) encephalitis in Thakurgaon District of northwest Bangladesh affected seven people, three of whom died. All subsequent cases developed illness 7-14 days after close physical contact with the index case while he was ill. Cases were more likely than controls to have been in the same room (100% vs. 9.5%, OR undefined, P<0.001) and to have touched him (83% vs. 0%, OR undefined, P<0.001). Although the source of infection for the index case was not identified, 50% of Pteropus bats sampled from near the outbreak area 1 month after the outbreak had antibodies to NiV confirming the presence of the virus in the area. The outbreak was spread by person-to-person transmission. Risk of NiV infection in family caregivers highlights the need for infection control practices to limit transmission of potentially infectious body secretions.

Disseminated infection with Bartonella henselae as a cause of spontaneous splenic rupture.

A 65-year-old man developed massive hemoperitoneum secondary to spontaneous splenic rupture. Histopathological analysis of the spleen demonstrated necrotizing granulomas. Results of serological tests indicated infection with a species of Bartonella, and immunohistochemical staining established Bartonella henselae as the cause of splenitis. To our knowledge, this represents the first reported case of spontaneous splenic rupture caused by infection with a species of Bartonella.

Serologic evidence of Rickettsia akari infection among dogs in a metropolitan city.

OBJECTIVE: To determine whether dogs in New York, NY are naturally infected with Rickettsia akari, the causative agent of rickettsialpox in humans. DESIGN: Serologic survey. ANIMALS: 311 dogs. PROCEDURE: Serum samples were obtained from dogs as a part of a study on Rocky Mountain spotted fever and borreliosis or when dogs were examined at area veterinary clinics for routine care. Dog owners were asked to complete a questionnaire inquiring about possible risk factors at the time serum samples were obtained. Samples were tested for reactivity to spotted fever group rickettsiae by use of an enzyme immunoassay (EIA). Twenty-two samples for which results were positive were tested by use of an indirect immunofluorescence antibody (IFA) assay followed by confirmatory cross-absorption testing. RESULTS: Results of the EIA were positive for 24 (7.7%) dogs. A history of tick infestation and increasing age were significantly associated with whether dogs were seropositive. Distribution of seropositive dogs was focal. Seventeen of the 22 samples submitted for IFA testing had titers to R rickettsii and R akari; for 11 of these, titers to R akari were higher than titers to R rickettsii. Cross-absorption testing indicated that in 6 of 7 samples, infection was caused by R akari. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that dogs can be naturally infected with R akari. Further studies are needed to determine the incidence of R akari infection in dogs, whether infection is associated with clinical illness, and whether dogs can serve as sentinels for human disease.

Urban zoonoses caused by Bartonella, Coxiella, Ehrlichia, and Rickettsia species.

The last half of the 20th Century witnessed an increase in the occurrence and recognition of urban zoonoses caused by members of the genera Bartonella, Coxiella, Ehrlichia, and Rickettsia, all traditionally considered to be members of the family Rickettsiaceae. In recent years, new human pathogens (Bartonella elizabethae, Bartonella henselae, and Rickettsia felis) have been recognized in urban environments. Other newly recognized pathogens (Ehrlichia chaffeensis and Ehrlichia phagocytophila in the United States) have sylvan zoonotic cycles but are present in urban areas because their vertebrate hosts and associated ectoparasitic arthropod vectors are able to survive in cities. Still other agents, which were primarily of historical importance (Bartonella quintana) or have not traditionally been associated with urban environments (Rickettsia rickettsii), have been recognized as causes of human disease in urban areas. Some diseases that have traditionally been associated with urban environments, such as rickettsialpox (caused by Rickettsia akari) and murine typhus (caused by Rickettsia typhi), still occur in large cities at low or undetermined frequencies and often go undetected, despite the availability of effective measures to diagnose and control them. In addition, alternate transmission cycles have been discovered for Coxiella burnetii, Rickettsia prowazekii, and R. typhi that differ substantially from their established, classic cycles, indicating that the epidemiology of these agents is more complex than originally thought and may be changing. Factors leading to an increase in the incidence of illnesses caused by these bacteria in urban areas include societal changes as well as intrinsic components of the natural history of these organisms that favor their survival in cities. Transovarial and transstadial transmission of many of the agents in their arthropod hosts contributes to the highly focal nature of many of the diseases they cause by allowing the pathogens to persist in areas during adverse times when vertebrate amplifying hosts may be scarce or absent. Domesticated animals (primarily cats, dogs, and livestock) or commensal rodents [primarily Norway rats (Rattus norvegicus) and house mice (Mus musculus)] can serve as vertebrate amplifying hosts and bring these agents and their ectoparasitic arthropod vectors into direct association with humans and help maintain transmission cycles in densely populated urban areas. The reasons for the increase in these urban zoonoses are complex. Increasing population density worldwide, shifts in populations from rural areas to cities, increased domestic and international mobility, an increase in homelessness, the decline of inner-city neighborhoods, and an increase in the population of immunosuppressed individuals all contribute to the emergence and recognition of human diseases caused by these groups of agents. Due to the focal nature of infections in urban areas, control or prevention of these diseases is possible. Increased physician awareness and public health surveillance support will be required to detect and treat existing urban infections caused by these agents, to determine the disease burden caused by them, to design and implement control programs to combat and prevent their spread, and to recognize emerging or resurging infections caused by members of these genera as they occur.

Fort Chaffee revisited: the epidemiology of tick-borne rickettsial and ehrlichial diseases at a natural focus.

A retrospective cohort study was conducted among troops training at Fort Chaffee, Arkansas, from May through June 1997, to identify infections caused by tick-borne pathogens. Serum samples were tested by IFAs for antibodies to selected Rickettsia and Ehrlichia species and by an investigational EIA for spotted fever group Rickettsia lipopolysaccharide antigens. Of 1,067 guardsmen tested, 162 (15.2%) had antibodies to one or more pathogens. Of 93 guardsmen with paired serum samples, 33 seroconverted to Rickettsia rickettsii or spotted fever group rickettsiae (SFGR) and five to Ehrlichia species. Most (84.8%) of the personnel who seroconverted to SFGR were detected only by EIA, and seropositivity was significantly associated with an illness compatible with a tick-borne disease. In addition, 34 (27%) of 126 subjects with detectable antibody titers reported a compatible illness. The primary risk factor for confirmed or probable disease was finding > 10 ticks on the body. Doxycycline use and rolling up of long sleeves were protective against seropositivity. The risk of transmission of tick-borne pathogens at Fort Chaffee remains high, and use of the broadly reactive EIA suggests that previous investigations may have underestimated the risk for infection by SFGR. Measures to prevent tick bite and associated disease may require reevaluation.

Evidence of rodent-associated Bartonella and Rickettsia infections among intravenous drug users from Central and East Harlem, New York City.

We tested serum samples collected in 1997 and 1998 from a cohort of 204 injection drug users (IDUs) recruited from Central and East Harlem, New York City, New York, for antibodies reactive with seven rickettsial or Bartonella spp. antigens. Rodent-associated Bartonella elizabethae and Rickettsia akari were the primary etiologic agents of interest. The testing panel also included Bartonella henselae, Bartonella quintana, Rickettsia prowazekii, Rickettsia rickettsii, and Rickettsia typhi. The highest prevalence of seroreactive serum samples (46%) was found with B. elizabethae antigens; 10% of the samples reacted with B. henselae antigens, while 2% reacted with B. quintana antigens. Reactivity to the latter two antigens was likely due to cross-reactivity with B. elizabethae antigens in most instances. Among the spotted fever group rickettsiae, 18 (9%) samples reacted with R. akari, including 10 samples (5%) that also reacted with R. rickettsii. Cross-adsorption studies demonstrated that most of the spotted fever group rickettsiae antibodies were due to R. akari infections. Among the typhus group rickettsiae, 5 samples reacted weakly to R. prowazekii antigens, and no samples reacted with R. typhi antigens. These findings suggest that Harlem IDUs are commonly exposed to two rodent-associated zoonotic agents. Further study of IDU populations may help elucidate transmission cycles of these agents in inner cities where higher levels of transmission occur.

Detection of antibodies reactive with Ehrlichia chaffeensis in the raccoon.

Antibodies reactive with Ehrlichia chaffeensis were detected in raccoon (Procyon lotor) serum samples by using an indirect immunofluorescence assay. Samples from 411 raccoons trapped in the southeastern United States from 1977 to 1999 were tested. Serologically reactive samples with reciprocal titers of > or =16 were detected from 83 raccoons (20%) from 13 of 16 counties in eight states, indicating that raccoons are commonly exposed to E. chaffeensis. Samples collected as early as 1977 were positive. A polymerase chain reaction assay specific for E. chaffeensis failed to detect the presence of ehrlichial DNA in serum samples from 20 representative seroreactive raccoons. Because of serologic cross-reactivity among antigens derived from different Ehrlichia spp., additional immunologic, molecular, or culture-based studies will be required to confirm E. chaffeensis infections of raccoons in the southeastern United States.

Serologic evidence of rickettsialpox (Rickettsia akari) infection among intravenous drug users in inner-city Baltimore, Maryland.

We tested single serum samples from 631 intravenous (i.v.) drug users from inner-city Baltimore, Maryland for serologic evidence of exposure to spotted fever group rickettsiae. A total of 102 (16%) individuals had titers > or = 64 to Rickettsia rickettsii by an indirect immunofluorescence assay. Confirmation that infection was caused by R. akari was obtained by cross-adsorption studies on a subset of serum samples that consistently resulted in higher titers to R. akari than to R. rickettsii. Current i.v. drug use, increased frequency of injection, and shooting gallery use were significant risk factors for presence of group-specific antibodies reactive with R. rickettsii. There was a significant inverse association with the presence of antibodies reactive to R. rickettsii and antibodies reactive to the human immunodeficiency virus. This study suggests that i.v. drug users are at an increased risk for R. akari infections. Clinicians should be aware of rickettsialpox, as well as other zoonotic diseases of the urban environment, when treating i.v. drug users for any acute febrile illness of undetermined etiology.

Serologic testing for human granulocytic ehrlichiosis at a national referral center.

An indirect immunofluorescence assay (IFA) was used to identify patients with antibodies reactive to the human granulocytic ehrlichiosis (HGE) agent. Serum samples collected from clinically ill individuals were submitted to the Centers for Disease Control and Prevention by physicians via state health departments from throughout the United States and tested against a panel of ehrlichial and rickettsial pathogens. Antibodies reactive to the HGE agent were detected in 142 (8.9%) of 1,602 individuals tested. There were 19 confirmed and 59 probable (n = 78) cases of HGE as defined by seroconversion or a fourfold or higher titer to the HGE agent than to the Ehrlichia chaffeensis antigens. The average age of patients with HGE was 57 years, and males accounted for 53 (68%) of the patients. Cases of HGE occurred in 21 states; 47 (60%) of the cases occurred in Connecticut (n = 14), New York (n = 18), and Wisconsin (n = 15). Onset of HGE was identified from April through December, with cases peaking in June and July. The earliest confirmed cases of HGE occurred in 1987 in Wisconsin and 1988 in Florida. No fatalities were reported among the 78 patients with confirmed or probable HGE. Reactivity to the HGE agent and to either Coxiella burnetii, Rickettsia rickettsii, or Rickettsia typhi was infrequent; however, 74 (52%) of the 142 individuals who were positive for HGE had at least one serum sample that also reacted to the E. chaffeensis antigen. Thirty-four persons with confirmed or probable human monocytic ehrlichiosis due to E. chaffeensis also had antibodies to the HGE agent in at least one serum sample. The specific etiologic agent for 30 patients was not ascribed because of similarity of titers to both ehrlichial antigens. The use of both antigens may be required to correctly diagnose most cases of human ehrlichiosis, especially in geographic regions where both the HGE agent and E. chaffeensis occur.

Diagnosis of human ehrlichiosis by PCR assay of acute-phase serum.

A PCR assay of 43 acute-phase serum samples was evaluated as a method for early detection of human granulocytic ehrlichiosis (HGE) and determination of etiology when serologic testing is inconclusive. Sequence-confirmed products of the HGE agent were amplified from three individuals residing or having exposure history in Minnesota or Wisconsin, and similarly confirmed products from Ehrlichia chaffeensis were amplified from three individuals from Florida or Maryland. Etiology, as determined by PCR and serology, was the same whenever there was a fourfold difference between the maximum titers of antibodies to both antigens, indicating that presumptive determination of etiology may be based on fourfold differences in titers. PCR testing determined that E. chaffeensis was the etiologic agent for one individual who had similar titers of antibodies to both agents. PCR assay of acute-phase serum in the absence of whole blood specimens may be a useful method for early detection of human ehrlichiosis and determination of etiology when serologic testing is inconclusive.

An indirect immunofluorescence assay using a cell culture-derived antigen for detection of antibodies to the agent of human granulocytic ehrlichiosis.

An indirect immunofluorescence assay for the detection of human antibodies to the agent of human granulocytic ehrlichiosis (HGE) was developed and standardized. Antigen was prepared from a human promyelocytic leukemia cell line (HL-60) infected with a tick-derived isolate of the HGE agent (USG3). Suitable antigen presentation and preservation of cellular morphology were obtained when infected cells were applied and cultured on the slide, excess medium was removed, and cells were fixed with acetone. Use of a buffer containing bovine serum albumin and goat serum reduced background fluorescence, and use of an immunoglobulin G (gamma-specific) conjugate reduced nonspecific binding. The assay readily detected specific antibody from HGE patients and did not detect antibody from healthy individuals. No significant reactivity was noted in sera from patients with high titers of antibodies to other rickettsial species. We were able to identify antibodies reactive to USG3 antigen in samples from areas where HGE is endemic that had tested negative to other rickettsial agents. Animal sera reactive against Ehrlichia equi or Ehrlichia phagocytophila bound to the HGE antigen, indicating that the assay may be useful for veterinary use. Comparability between two different laboratories was assessed by using coded human sera exchanged between laboratories. Results from the two laboratories were similar, indicating that the assay can be easily integrated into use for routine testing for HGE. The assay was then compared to an assay using horse neutrophils infected with ehrlichiae. The two assays gave comparable results, indicating that the cell culture-derived antigen can be used for testing samples that have been previously tested with E. equi as an antigen. The new assay offers several advantages over other immunofluorescence methods that use animal-derived antigen and is suitable for use in testing for human antibodies to the HGE agent.

Antibodies to Bartonella species in inner-city intravenous drug users in Baltimore, Md.

BACKGROUND: Bartonella quintana has recently been associated with homeless alcoholic men. Both B quintana and Bartonella henselae have been shown to be opportunistic pathogens of people with acquired immunodeficiency syndrome. The reservoirs and modes of transmission of these infections are incompletely known. OBJECTIVES: To examine serum samples that were taken from inner-city intravenous (IV) drug users for antibodies to Bartonella organisms to determine whether there is an urban transmission cycle for Bartonella species and to examine the demographic and behavioral characteristics of IV drug users to identify possible risk factors for infection with any of these agents. MATERIALS AND METHODS: A serologic survey was conducted, using a convenience sample of serum specimens collected during a study of IV drug use and human immunodeficiency virus infection among 630 inner-city residents in Baltimore, Md. A detailed questionnaire was administered at the initial collection of serum, and additional serum collections and questionnaire updates were made at 6-month intervals. The most recent available serum sample was tested for Bartonella antibody titer by using the indirect immunofluorescent antibody test with 3 antigens: Bartonella elizabethae, B henselae, and B quintana. Univariate and multivariate analyses of selected potential demographic and behavioral risk factors were conducted. RESULTS: Antibodies to Bartonella were highly prevalent in this group; more than 37% of all samples reacted with at least 1 antigen. Overall seroprevalence of antibodies to B elizabethae, B henselae, and B quintana was 33%, 11%, and 10%, respectively. Current IV drug use, frequency of injection, and seronegative human immunodeficiency virus status were significantly associated with Bartonella antibody presence, but these associations varied by analysis. There was a significant inverse association of antibody prevalence to B henselae and B quintana by using CD4+ cell counts among human immunodeficiency virus-seropositive individuals. CONCLUSIONS: Intravenous drug users have an elevated prevalence of antibodies to Bartonella organisms and may be at significant risk of becoming infected. Current IV drug use, high frequency of injection, and seronegative human immunodeficiency virus status are significant risk factors for an increased prevalence of Bartonella antibodies. The current natural histories of Bartonella species are rapidly changing, and mechanisms of transmission remain unknown.

Incompetence of white-tailed deer as amplifying hosts of vesicular stomatitis virus for Lutzomyia shannoni (Diptera: Psychodidae).

Sand flies, Lutzomyia shannoni Dyar, were allowed to feed on 3 white-tailed deer, Odocoileus virginiana Zimmermann, that previously had been infected with the New Jersey serotype of vesicular stomatitis (VSNJ) virus. Flies fed in the lower abdominal area of each deer on days 1-5 postinfection. A blood sample, nasal swab, and throat swab were taken during each feeding trial and examined for virus. Blood-fed flies were held for 4-5 d following the bloodmeal and tested for VSNJ virus infection. VSNJ virus was never detected in blood or from swabs taken from infected deer nor from any of the sand flies that fed on deer. The findings suggest that white-tailed deer do not fulfill the traditional concept of amplifying hosts of VSNJ virus.

Incompetence of domestic pigs as amplifying hosts of vesicular stomatitis virus for Lutzomyia shannoni (Diptera: Psychodidae).

Seven domestic pigs, Sus scrofa L., were infected by intradermal inoculation at 3 different sites with the New Jersey serotype of vesicular stomatitis (VSNJ) virus. Laboratory-reared Lutzomyia shannoni Dyar sand flies, a suspected biological vector of VSNJ virus, were allowed to feed on pigs at the lower abdomen or at sites of their own selection on days 1-7 and on day 10 postinfection. Blood samples were taken from infected swine concomitant with most feeding trials and tested for the presence of virus. Sand flies were held for up to 5 d following ingestion of blood and tested for VSNJ virus infection. Virus was not recovered from the blood of infected pigs or from any of the flies that fed on these pigs. The findings suggest that domestic pigs do not fulfill the traditional concept of amplifying hosts of VSNJ virus.

Population dynamics of Lutzomyia shannoni (Diptera: Psychodidae) in relation to the epizootiology of vesicular stomatitis virus on Ossabaw Island, Georgia.

Population dynamics of Lutzomyia shannoni Dyar were studied on Ossabaw Island, GA, to define further the role of this species in the epizootiology of the New Jersey serotype of vesicular stomatitis (VSNJ) virus. Bimonthly collections of sand flies egressing from hollow trees from April to November 1991 indicated that there were three generations of sand flies. Data from light trap collections from 1986 through 1989 indicated that similar seasonal cycles occurred during previous years. At this site, we hypothesize that L. shannoni undergoes facultative diapause. Two isolates of VSNJ virus were obtained from female sand flies collected in May and June of 1991. We believe that the virus overwinters in immature L. shannoni and that transovarially infected sand flies emerging each spring initiate a summer amplification cycle in swine on Ossabaw Island.

Hosts of Lutzomyia shannoni (Diptera: Psychodidae) in relation to vesicular stomatitis virus on Ossabaw Island, Georgia, U.S.A.

Hosts of Lutzomyia shannoni Dyar, a suspected biological vector of the New Jersey serotype of vesicular stomatitis (VSNJ) virus, were determined using an indirect enzyme-linked immunosorbent assay (ELISA) of 333 blood-fed female sandflies collected from their diurnal resting shelters on Ossabaw Island, Georgia, U.S.A. Sandflies had fed primarily on white-tailed deer (Odocoileus virginianus) (81%) and to a lesser extent on feral swine (Sus scrofa) (16%), two species of host infected annually with VSNJ. Other hosts were raccoons (Procyon lotor) and horses (Equus caballus) or donkeys (E. asinus), with only two (< 1%) mixed bloodmeals from deer/raccoon and deer/swine. A larger proportion of feedings on feral swine was detected in maritime live oak forests than in mixed hardwood forests. These findings are consistent with the hypothesis that L.shannoni is a primary vector of VSNJ virus on Ossabaw Island.

Feral swine as a potential amplifying host for vesicular stomatitis virus New Jersey serotype on Ossabaw Island, Georgia.

Sentinel feral swine (Sus scrofa) on Ossabaw Island, Georgia (USA), were serologically monitored for antibodies to vesicular stomatitis New Jersey serotype (VSNJ) virus from 17 April to 27 August 1990. Seroconversions to VSNJ virus were detected in 24% of swine island-wide. Differences in the incidence of seroconversion were detected between swine sampled in the Pleistocene and Holocene formations of the island suggesting that the presence of virus is forest type dependent. Based on the consistency in onset and spatial distribution of seroconversions with data from 1981 to 1985, this is a very stable host-parasite system. Sequential virus isolation attempts from nasal swabs, tonsil swabs, and blood were made on a subsample of 54 sentinel swine from 9 May to 4 July 1990. The VSNJ virus was isolated from five swine from 16 May to 20 June. Vesicular lesions were detected on only two of these animals. Although infections in these feral swine were short-lived (< 7 days) and were followed by a strong neutralizing antibody response, VSNJ virus was detected in a single group of swine for a period exceeding 1 month. From these data, it appears that feral swine could provide a source of virus to feeding arthropods for extended periods of time. The failure to detect a viremia in these animals, however, indicates that a source other than blood may be required for transmission to occur.

Effect of forest type on the distribution of Lutzomyia shannoni (Diptera: Psychodidae) and vesicular stomatitis virus on Ossabaw Island, Georgia.

We studied the effects of three forest types on multiple factors that are believed to influence the transmission of the New Jersey serotype of vesicular stomatitis (VSNJ) virus on Ossabaw Island, GA. These factors included availability of tree hole diurnal resting habitat for the presumed sand fly vector, Lutzomyia shannoni Dyar; relative abundance of L. shannoni; prevalence of VSNJ virus infection in sand flies; and prevalence of VSNJ virus antibodies in wild swine. Tree hole availability, sand fly abundance, and antibody prevalence in swine were significantly greater in maritime live oak forest than in other forest types. A single isolate of VSNJ virus was obtained from sand flies collected in maritime live oak forest. These data indicate that the relative abundance of adult L. shannoni is influenced significantly by the availability of tree holes and that VSNJ virus infection in wild swine is linked to forest type and is greatest in areas capable of supporting abundant populations of L. shannoni.

Seasonal abundance of Lutzomyia shannoni (Diptera: Psychodidae) on Ossabaw Island, Georgia.

Population dynamics of Lutzomyia shannoni were monitored from April 1986 through December 1987 on Ossabaw Island, Ga. Most (99%) of the 19,788 adult sand flies were collected in light traps supplemented with dry ice; less than or equal to 1% were aspirated from diurnal resting sites. Adult sand flies first appeared in April and were followed by peaks of abundance during May 1986, and May and July 1987. Numbers of adults captured fell rapidly in October and November 1986 and in September and October 1987. No specimens were collected in December 1986 or in March, November, and December 1987. Light trap catch was affected positively by mean nightly air temperature and negatively by rainfall 14 d before collection, but not by wind speed or moon phase. Vesicular stomatitis viral activity, as measured by antibodies in feral and domestic swine, roughly corresponded to the seasonal appearance of adult L. shannoni during 1986 and 1987. Significantly more adults (72%) were collected in light traps at ground level (0.5m) than at heights of 4 and 8m. Most resting adults were collected from dark, moist tree holes and cavities of various hardwoods.

Titers of vesicular stomatitis virus, New Jersey serotype, in naturally infected male and female Lutzomyia shannoni (Diptera: Psychodidae) in Georgia.

Seven isolates of the New Jersey serotype of vesicular stomatitis (VSNJ) virus were obtained from pooled specimens of phlebotomine sand flies, Lutzomyia shannoni Dyar, collected on Ossabaw Island, Chatham County, Ga., in 1989 and 1990. Three isolates, including two from males, were obtained from light-trapped sand flies in 1989. Four isolates were obtained from pools of sand flies collected from hollow trees in 1990. Three of the latter pools contained from 4.0 to 4.7 log10 of plaque-forming units of virus per ml, suggesting that the positive flies in these pools had supported VSNJ virus replication. One of these high-titered isolates was obtained from a pool of male sand flies. These data provide further support for the hypotheses that L. shannoni is a biological vector of VSNJ virus at this enzootic focus and that transovarial transmission of the virus occurs in nature.