Seroprevalence and seroincidence of Leptospira infection in dogs during a one-year period in an endemic urban area in Southern Brazil

INTRODUCTION: Leptospirosis is a zoonosis that affects both humans and animals. Dogs may serve as sentinels and indicators of environmental contamination as well as potential carriers for Leptospira. This study aimed to evaluate the seroprevalence and seroincidence of leptospirosis infection in dogs in an urban low-income community in southern Brazil where human leptospirosis is endemic. METHODS: A prospective cohort study was designed that consisted of sampling at recruitment and four consecutive trimestral follow-up sampling trials. All households in the area were visited, and those that owned dogs were invited to participate in the study. The seroprevalence (MAT titers ≥100) of Leptospira infection in dogs was calculated for each visit, the seroincidence (seroconversion or four-fold increase in serogroup-specific MAT titer) density rate was calculated for each follow-up, and a global seroincidence density rate was calculated for the overall period. RESULTS: A total of 378 dogs and 902.7 dog-trimesters were recruited and followed, respectively. The seroprevalence of infection ranged from 9.3% (95% CI; 6.7 - 12.6) to 19% (14.1 - 25.2), the seroincidence density rate of infection ranged from 6% (3.3 - 10.6) to 15.3% (10.8 - 21.2), and the global seroincidence density rate of infection was 11% (9.1 - 13.2) per dog-trimester. Canicola and Icterohaemorraghiae were the most frequent incident serogroups observed in all follow-ups. CONCLUSIONS: Follow-ups with mean trimester intervals were incapable of detecting any increase in seroprevalence due to seroincident cases of canine leptospirosis, suggesting that antibody titers may fall within three months. Further studies on incident infections, disease burden or risk factors for incident Leptospira cases should take into account the detectable lifespan of the antibody. .

Seroincidence of Human Herpes Virus 2 Among Ante-natal Clinic Attendees in Benin, Nigeria.

Background: Human Herpes Virus 2 (HSV-2) infection has been shown to be significantly associated with several obstetric complications, especially if the infection occurred during the pregnancy. Advocacy for policy formulation and the design of interventions requires local data on the risk factors for incident HSV-2 infection. The aim of this study is to assess HSV-2 sero-incidence among pregnant women in Benin and the effect of socio-demographic factors, HIV status, and HSV-1 status. Study Location, Design and Duration: Pregnant women attending ante-natal clinic in University of Benin Teaching Hospital and Central Hospital, Benin were prospectively recruited. A cross-sectional study was done and baseline data, obtained. The HSV-2 seronegative participants were followed up till the last clinic appointments [the closest appointment to their expected delivery dates (EDD)]. The study took place between November 2011 and December 2012. Methods: On recruitment a structured self-administered questionnaire was used to capture their socio-demographic data. Obstetric data was obtained from the patients’ case notes. Their HSV-1 and HSV-2 serostatuses were determined using an HSV glycoprotein G-based type-specific ELISA technique. Their HIV statuses were also determined. All those who were seronegative for HSV-2 were retested for HSV-2 six months later and/or on their last clinic appointment before the EDD. Incidence rates were calculated per person-years. Data analysis utilized SPSS version 16 software. Results: Out of the 674 participants, 315(46.8%) were HSV-2 seropositive while 359 (53.2%) were seronegative. 15.9% (57) of the HSV-2 sero-negative ones were lost to follow-up, giving a response rate of 84.1%. Seroincidence rate was found to be 17.9 per 100 person-years. There was significant association of seroincidence with younger reproductive age groups, unmarried status, and education below secondary level. Relative Risk (RR) and Incidence rate ratio (IRR) of HSV-2 infection among the HIV-infected cohort were 55.15 [95%CI:17.0-179.1] and 72.37 [95% CI:71.11-73.63] respectively. The RR and IRR among the HSV-1-seronegative cohort were 1.43 [95%CI:0.64-3.17] and 11.62 [95%CI:9.60-13.64] respectively. Conclusion: Seroincidence rate of HSV-2 infection among pregnant women in Benin was found to be 17.9 per 100 person-years. Positive HIV status, young age, unmarried status, and low education level were indicators of increased risk of incident HSV-2 infection.

Sero-survey on Aino, Akabane, Chuzan, bovine ephemeral fever and Japanese encephalitis virus of cattle and swine in Korea

Vector-borne arboviruses produce mild to severe symptoms in domestic animals. Bovine ephemeral fever (BEF), Akabane, Aino, and Chuzan virus have been primarily attributed to reproductive disorders or febrile diseases in cattle, and Japanese encephalitis virus (JEV) is mainly associated with reproductive failures in swine. We investigated antibody titers from domestic swine against four bovine arboviruses (BEF, Akabane, Aino, and Chuzan virus) and from cattle against JEV in Korea. While the positive rates for Akabane and BEF were 37.4% and 15.7%, the positive incidence of Chuzan and Aino were relatively low, with positive rates of 3.04% and 0.4%, respectively, based on a virus neutralization assay. Antibody titers against more than one virus were also frequently detected in domestic swine. The incidence of JEV was 51.3% among domestic cattle. In addition, one positive case was detected in the thoracic fluids from 35 aborted calves, based on the hemagglutination inhibition test. Our results indicate that swine are susceptible hosts of bovine arboviruses without showing clinical symptoms in a natural environment. Moreover, we confirmed that JEV could be associated with reproductive failure in pregnant cattle, as were other vector-borne bovine arboviruses assessed in this study.

Seroincidence of Hepatitis B Virus among Korean Blood Donors / 대한수혈학회지

BACKGROUND: Seroincidence of hepatitis B virus (HBV) among Korean blood donors has not been reported. This study was conducted to calculate the seroincidence of HBV among blood donors and to estimate the risk of post-transfusion hepatitis B by donated blood in window period of infection. METHODS: HBV seroincidence was calculated among repeat-donors who had donated from Nov. 1994 through Dec. 1996. To calculate the person-years, the database of the Korean National Red Cross was used in which results for HBsAg enzyme immunoassay were filed up. The observed incidence was adjusted by interdonation interval of incident cases, who were defined as donors showing seroconversion. The risk of post-transfusion hepatitis B by donated bloods in window period of infection was estimated. RESULTS: HBV seroincidence was estimated to be 180.85/100,000 person-years. This was adjusted as 602.83/100,000 person-years by considering interdonation intervals. The risk of post-transfusion hepatitis B was estimated to be 974 units per one million of whole blood units due to be in window period of infection. CONCLUSION: The estimated seroincidence of HBV among Korean blood donors and thereby the risk of HBV transmission by donated bloods in window period of infection was about 50 to 60 times higher than those of Japan and United States of America.

Seroincidence of Hepatitis B Virus among Korean Blood Donors

BACKGROUND: Seroincidence of hepatitis B virus (HBV) among Korean blood donors has not been reported. This study was conducted to calculate the seroincidence of HBV among blood donors and to estimate the risk of post-transfusion hepatitis B by donated blood in window period of infection. METHODS: HBV seroincidence was calculated among repeat-donors who had donated from Nov. 1994 through Dec. 1996. To calculate the person-years, the database of the Korean National Red Cross was used in which results for HBsAg enzyme immunoassay were filed up. The observed incidence was adjusted by interdonation interval of incident cases, who were defined as donors showing seroconversion. The risk of post-transfusion hepatitis B by donated bloods in window period of infection was estimated. RESULTS: HBV seroincidence was estimated to be 180.85/100,000 person-years. This was adjusted as 602.83/100,000 person-years by considering interdonation intervals. The risk of post-transfusion hepatitis B was estimated to be 974 units per one million of whole blood units due to be in window period of infection. CONCLUSION: The estimated seroincidence of HBV among Korean blood donors and thereby the risk of HBV transmission by donated bloods in window period of infection was about 50 to 60 times higher than those of Japan and United States of America.(Korean J Blood Transfusion 10(1): 1-4, 1999)

Study on the Seroincidence of Hepatitic C Virus Infection among blood donors in Korea / 대한수혈학회지

BACKGROUND: Since the introduction of anti-HCV assay, post-transfusion hepatitis (PTH) by Hepatitis C Virus (HCV) was remakably reduced. Recently, based on the estimation of HCV seroincidence rate in blood donors, an investigator insisted that alanine aminotransferase (ALT) test be discontinued as a surrogate marker. This study was designed to determine the HCV seroincidence in Korean blood donors. METHODS: HCV seroincidence was calculated using repeat donors who had donated repeatedly during the 26 months from Nov. 1994 through Dec. 1996. To calculate the person-years according to ALT value, the computer database of the Korean National Red Cross (KNRC) was used in which results for anti-HCV by enzyme immunoassay (EIA) were filed up. To count the true incidence cases, who were defined as donors showing seroconversion by confirmatory test in two successive donation, seroconverted donors by EIA were individually reconfirmed whether they were true seroconverters. Finally, projected impact on HCV risk of discontining of ALT screening was calculated by using two important value previously known, such as periods of seroconversion window for anti-HCV and ALT preconversion window. RESULTS: HCV seroincidence was estimated to be 13.79/100,000 person-years. Seroincidences according to the ALT groups were as follows; 13.22 in the normal ALT group ( or =131 IU/L). By this study, investigators also could find seroconverted donors, whose result for anti-HCV by immunoblot was positive at the first donation and changed to negative by EIA at the next donation, as many as 100 donors. Among these falsely seroconverted persons, 16% of donors showed elevated ALT value. 8 units per 1 million donations were estimated to be discarded only by abnormal results of ALT testing in Korea. CONCLUSION: HCV seroincidence in Korean donors was 2.8 times as high as in American donors. HCV seroincidence calculated by this study seems to be somewhat lower than true rate because of the problem of summing-up the person-years. Considering that higher seroincidence results in more donors in seroconversion window phase, donor selection by careful history taking should be re-emphasized to reduce the seroincidence rate in Korean blood donation program.