The American Journal of Tropical Medicine and Hygiene - Volume 87, Issue 1, July 2012

Tungiasis is a zoonosis caused by Tunga penetrans. In Brazil, tungiasis is endemic in many resource-poor communities, in which various domestic and sylvatic animals act as reservoirs. Eighty laboratory-raised Wistar rats were exposed to T. penetrans in areas of intense transmission: a fishing village and an urban shantytown in Ceará State, northeast Brazil. The topographic distribution of lesions in Wistar rats was compared with the distribution of lesions in humans in the same area. Our results show that the topographic distribution of embedded sand fleas was almost identical in Wistar rats and humans and that lesions were confined to the feet. In humans, 76% of all lesions were located periungually, whereas in Wistar rats, 67% of lesions were located at the distal end of the digits (P = 0.73). Both had the majority of lesions at the toes and digits: 70.2% versus 65.7% (P = 0.79). The Wistar rat model mirrors human tungiasis in topographic distribution.

Febrile illnesses remain a major cause of morbidity and mortality in resource-poor countries, but too often, tests are not available to determine the causes, leading to misdiagnosis and inappropriate treatment. To determine the cause of febrile illnesses, we recovered the malaria smears from 102 children presenting with fever to Soddo Christian Hospital in Wolaitta Soddo, Ethiopia. DNA was isolated from the smears and evaluated by real-time polymerase chain reaction. We identified pathogen DNA with probes for Plasmodium spp., Streptococcus pneumoniae, Rickettsia spp., Salmonella spp., and Borrelia spp. Overall, we showed that it is possible to isolate high-quality DNA and identify treatable pathogens from malaria blood smears. Furthermore, our data showed that bacterial pathogens (especially Pneumococcus, Rickettsia spp., and Borrelia spp.) are common and frequently unrecognized but treatable causes of febrile illnesses in Ethiopian children.

Our objective was to identify local animal reservoirs of leptospirosis to explain the unusual features of Leptospira strains recently described among patients on the island of Mayotte. By means of a microscopic agglutination test using local clinical isolates, we found that 11.2% of black rats were seropositive to Leptospira, whereas 10.2% of flying foxes, 2% of lemurs, 93.1% of domestic dogs, and 87.5% of stray dogs were seropositive. As observed in humans, Mini was the main serogroup circulating in animals, whereas serogroup Icterohaemorrhagiae was absent. Using quantitative polymerase chain reaction, we also showed that 29.8% of rats carried leptospires in their kidneys. The sequencing of 16S rRNA gene sequences of Leptospira found in black rat kidneys identified four genomospecies (Leptospira borgpetersenii, Leptospira interrogans, Leptospira kirschneri, and L. borgpetersenii group B), which established black rats as the major source of leptospirosis transmission to humans. The origins of such a genetic diversity in Leptospira strains are discussed.

Clinical information regarding murine typhus in Taiwan is limited. In this study, 81 cases of serologically documented murine typhus during 1992–2009 at four referral hospitals in southern Taiwan were analyzed. There was a significant correlation between average environmental temperature and case numbers of murine typhus (r = 0.747, P = 0.005). Acute hepatitis was found in 67% of cases, and hyperbilirubinemia (serum total bilirubin ≥ 23.9 μmol/L) was found in 38%. The intervals between the initiation of appropriate therapy to defervescence were longer in patients with hyperbilirubinemia than those without hyperbilirubinemia (6.1 versus 4.1 days; P = 0.015). Nine (11.1%) showed development of severe illnesses such as acute respiratory distress syndrome (2 patients), aseptic meningitis (3), and acute renal failure (4). Only one died of acute respiratory distress syndrome. Cases of murine typhus were often found during the summer and had acute febrile hepatitis. Those patients with hyperbilirubinemia tended to have a delayed recovery even with appropriate therapy.

We evaluated the diagnostic accuracy of two broadly reactive rapid immunochromatographic tests (ICTs) for detection of IgM and IgG against Orientia tsutsugamushi by using archived acute-phase serum samples from 102 patients with laboratory-confirmed scrub typhus, and from 62 archived serum samples from patients with other causes of fever as a negative control. These ICTs were constructed by using a mixture of recombinant proteins: 1) C1, a chimeric protein containing epitopes of the 56-kD antigen from Karp and TA763 strains; 2) Ktr56; and 3) Gmr56. Sensitivities of the ICTs for detection of IgM and IgG were 90.2% (95% confidence interval [CI] = 84.4–96.0%) and 86.3% (95% CI = 80.9–93.8%), respectively. Specificities were 85.5% (95% CI = 73.9–92.2%) and 96.8% (95% CI = 90.3–100%), respectively. Both assays were more sensitive and specific than the standard immune immunofluorescence assay for the early diagnosis of scrub typhus.

Pyrazinamidase of Mycobacterium tuberculosis catalyzes the conversion of pyrazinamide to the active molecule pyrazinoic acid. Reduction of pyrazinamidase activity results in a level of pyrazinamide resistance. Previous studies have suggested that pyrazinamidase has a metal-binding site and that a divalent metal cofactor is required for activity. To determine the effect of divalent metals on the pyrazinamidase, the recombinant wild-type pyrazinamidase corresponding to the H37Rv pyrazinamide-susceptible reference strain was expressed in Escherichia coli with and without a carboxy terminal. His-tagged pyrazinamidase was inactivated by metal depletion and reactivated by titration with divalent metals. Although Co2+, Mn2+, and Zn2+ restored pyrazinamidase activity, only Co2+ enhanced the enzymatic activity to levels higher than the wild-type pyrazinamidase. Cu2+, Fe2+, Fe3+, and Mg2+ did not restore the activity under the conditions tested. Various recombinant mutated pyrazinamidases with appropriate folding but different enzymatic activities showed a differential pattern of recovered activity. X-ray fluorescence and atomic absorbance spectroscopy showed that recombinant wild-type pyrazinamidase expressed in E. coli most likely contained Zn. In conclusion, this study suggests that M. tuberculosis pyrazinamidase is a metalloenzyme that is able to coordinate several ions, but in vivo, it is more likely to coordinate Zn2+. However, in vitro, the metal-depleted enzyme could be reactivated by several divalent metals with higher efficiency than Zn.

In this report, we present a case of isolated liver tuberculosis (TB) as a cause of non-cirrhotic portal hypertension leading to bleeding esophageal varices. Although TB has been known to cause portal hypertension in a variety of ways, this case was notable for the presence of periportal inflammation and granulomas, also seen in hepatic schistosomiasis. Herein, we discuss isolated liver TB and the differential diagnosis of non-cirrhotic portal hypertension. In endemic areas, TB should be considered in the differential diagnosis of non-cirrhotic portal hypertension.

Non-invasive specimens for dengue diagnosis may be preferable where venous blood is difficult to collect and/or process, such as community-based or remote settings or when sampling from young children. We evaluated the performance of oral swabs and dried blood spots (DBS), compared with plasma, in diagnosing acute dengue and screening for past dengue virus (DENV) exposure. DENV-specific immunoglobulin (Ig) M, IgG, and NS1 antigen were detected both in oral swabs and DBS from acute patients. Oral swabs were less sensitive (IgM: 68.7%, IgG: 91.9%, NS1: 64.7%), but retained good specificity (100%, 92.3%, 95.8%, respectively) compared with plasma. DBS displayed high sensitivity (IgM: 100%, IgG: 96%, NS1: 100%) and specificity (IgM: 75%, IgG: 93%). DENV RNA was amplified from DBS (sensitivity 95.6%) but not from oral swabs. DENV-IgG (indicative of past flavivirus exposure) were detected with moderate sensitivity (61.1%) but poor specificity (50%) in oral swabs from healthy volunteers. Dried blood spots allow sensitive and specific diagnosis of acute dengue by serological, molecular, and antigen detection methods. Oral swabs may be an adequate alternative where blood cannot be collected.

Japanese encephalitis virus (JEV) is a major cause of encephalitis in Asia. We estimated the diagnostic accuracy of two anti-JEV immunoglobulin M (IgM) enzyme-linked immunosorbent assays (ELISAs) (Panbio and XCyton JEVCheX) compared with a reference standard (AFRIMS JEV MAC ELISA) in a prospective study of the causes of central nervous system infections in Laos. Cerebrospinal fluid (CSF; 515 patients) and serum samples (182 patients) from those admitted to Mahosot Hospital, Vientiane, were tested. The CSF from 14.5% of acute encephalitis syndrome (AES) patients and 10.1% from those with AES and meningitis were positive for anti-JEV IgM in the reference ELISA. The sensitivities for CSF were 65.4% (95% confidence interval [CI] = 51–78) (Xcyton), 69.2% (95% CI = 55–81) (Panbio), however 96.2% (95% CI = 87–100) with Panbio Ravi criteria. Specificities were 89–100%. For admission sera from AES patients, sensitivities and specificities of the Panbio ELISA were 85.7% (95% CI = 42–100%) and 92.9% (95% CI = 83–98%), respectively.

We conducted enhanced surveillance to identify medical risk factors for severe illness (i.e., hospitalization or death) and neuroinvasive disease (i.e., encephalitis or meningitis) among all West Nile virus disease cases reported from selected states from 2008 to 2010. Of the 1,090 case-patients included in the analysis, 708 (65%) case-patients were hospitalized, 641 (59%) case-patients had neuroinvasive disease, and 55 (5%) case-patients died. Chronic renal disease (adjusted odds ratio [aOR] = 4.1; 95% confidence interval [CI] = 1.4–12.1), history of cancer (aOR = 3.7; 95% CI = 1.8–7.5), history of alcohol abuse (aOR = 3.0; 95% CI = 1.3–6.7), diabetes (aOR = 2.2; 95% CI = 1.4–3.4), and hypertension (aOR = 1.5; 95% CI = 1.1–2.1) were independently associated with severe illness on multivariable analysis. Although the same medical conditions were independently associated with encephalitis, only hypertension was associated with meningitis. The only condition independently associated with death was immune suppression. Prevention messages should be targeted to persons with these conditions.

A nationwide epidemiologic investigation of domestic animal infections has been conducted in nine provinces and one city during 2007–2010. Serum samples from a total of 707 goats, 433 cattle, and 219 dogs were collected for detecting Anaplasma phagocytophilum IgG antibody by immunofluorescence assays and the average seroprevalences were 10.05% for dogs, 3.82% for goats, and 0.69% for cattle, respectively. A total of 472 goats, 201 cattle, 102 dog blood clots, and 1,580 ticks were collected for polymerase chain reaction (PCR) amplifying A. phagocytophilum 16S rRNA genes and the PCR-positive rates were 26.69% for goats, 23.38% for cattle, and 10.89% for dogs. Six species were identified and the average PCR-positive rates were 58.3% for Dermacentor silvarum, 43.9% for Haemaphysalis longicornis, 12.5% for Ixodes persulcatus, 7.5% (3 of 40) for Boophilus microplus, and 5.2% for Rhipicephalus sanguineus, respectively. The evidence in the study indicated the zoonotic Rickettsia is highly prevalent in China.