Leptospirosis: a diagnostic conundrum.

Leptospirosis is a serious public health concern worldwide. It is highly endemic in the Andaman Islands and its prevalence is increasing in other Indian states. Clinical features are non-specific and diagnosis relies on laboratory confirmation. The gold standard is microscopic agglutination testing, but this is not widely available. Real-time polymerase chain reaction testing of LipL32 antigen provides the earliest detection of pathogenic Leptospira in the body. We found it to be 100% specific, but it should be used in the first 10 days of illness for reliable results.

Evaluación de un panel reducido de cepas de leptospiras para el diagnóstico en humanos por microaglutinación (MAT) / Evaluation of a reduced panel of leptospira strains for microagglutination

Objetivo. Evaluar si el uso del panel de 19 cepas de leptospiras, sugerido por la Sociedad Internacional de Leptospirosis para la microaglutinación (MAT, por sus siglas en inglés), permite mayor confirmación de casos que el de 12 cepas. Material y métodos. Estudio observacional de corte transversal. Se estudiaron 441 muestras de sueros de pacientes de Argentina, derivadas para el diagnóstico de leptospirosis en los periodos de julio de 2009 a diciembre de 2010 y enero a octubre de 2013. Resultados. Se obtuvo el mismo resultado con el panel reducido que con el ampliado. En seis casos resultó presumiblemente infectante algún serovar del panel ampliado, aunque siempre coaglutinando con cepas del reducido. Conclusión. En Argentina, el diagnóstico de leptospirosis por MAT podría continuar realizándose con el panel reducido, lo que reduciría el costo y tiempo de diagnóstico. La información adicional que aportaría el panel ampliado está relacionada con la epidemiología, mediante un mejor conocimiento del serogrupo presumiblemente infectante.

Objective. To evaluate if the use of the 19 Leptospira strains panel suggested by the International Leptospirosis Society of World Health Organization for microagglutination allows confirmation of more cases that the 12 strains panel used in Argentina. Materials and methods. Cross-sectional observational study. We studied 441 serum samples corresponding to Argentinean patients with suspected leptospirosis derived during from July to December, 2009 and from January to October, 2013. Results. The same number of positive samples was obtained using the MAT with the 19 or 12 strains. In six cases a serovar of the expanded collection was presumably infecting, but always coagglutinated with strains of the reduced panel. Conclusion. In Argentina, the diagnosis of leptospirosis by MAT could be made using the reduced 12 strains panel, obtaining the same result in case detection as using the 19 strains panel. Additional information provided by the use of all strains could be the presumably infecting serogroup.

Sensitivity and specificity of HAT Sero-K-SeT, a rapid diagnostic test for serodiagnosis of sleeping sickness caused by Trypanosoma brucei gambiense: a case-control study.

BACKGROUND: Human African trypanosomiasis (HAT) is a life-threatening infection affecting rural populations in sub-Saharan Africa. Large-scale population screening by antibody detection with the Card Agglutination Test for Trypanosomiasis (CATT)/Trypanosoma brucei (T b) gambiense helped reduce the number of reported cases of gambiense HAT to fewer than 10 000 in 2011. Because low case numbers lead to decreased cost-effectiveness of such active screening, we aimed to assess diagnostic accuracy of a rapid serodiagnostic test (HAT Sero-K-SeT) applicable in primary health-care centres. METHODS: In our case-control study, we assessed participants older than 11 years who presented for HAT Sero-K-SeT and CATT/T b gambiense at primary care centres or to mobile teams (and existing patients with confirmed disease status at these centres) in Bandundu Province, DR Congo. We defined cases as patients with trypanosomes that had been identified in lymph node aspirate, blood, or cerebrospinal fluid. During screening, we recruited controls without previous history of HAT or detectable trypanosomes in blood or lymph who resided in the same area as the cases. We assessed diagnostic accuracy of three antibody detection tests for gambiense HAT: HAT Sero-K-SeT and CATT/T b gambiense (done with venous blood at the primary care centres) and immune trypanolysis (done with plasma at the Institute of Tropical Medicine, Antwerp, Belgium). FINDINGS: Between June 6, 2012, and Feb 25, 2013, we included 134 cases and 356 controls. HAT Sero-K-SeT had a sensitivity of 0·985 (132 true positives, 95% CI 0·947-0·996) and a specificity of 0·986 (351 true negatives, 0·968-0·994), which did not differ significantly from CATT/T b gambiense (sensitivity 95% CI 0·955, 95% CI 0·906-0·979 [128 true positives] and specificity 0·972, 0·949-0·985 [346 true negatives]) or immune trypanolysis (sensitivity 0·985, 0·947-0·996 [132 true positives] and specificity 0·980, 0·960-0·990 [349 true negatives]). INTERPRETATION: The diagnostic accuracy of HAT Sero-K-SeT is adequate for T b gambiense antibody detection in local health centres and could be used for active screening whenever a cold chain and electricity supply are unavailable and CATT/T b gambiense cannot be done.

An evaluation of the performance of direct agglutination test on filter paper blood sample for the diagnosis of visceral leishmaniasis.

The attack phase of the visceral leishmaniasis (VL) elimination program in Bangladesh aims to decrease the burden of VL incidence from close to 20 cases to less than one case per 10,000 at sub-district level. The consolidation phase will aim to confirm no increase in VL in endemic areas through active surveillance. During this phase, a reliable diagnostic tool for mass screening is required. Here, we report the diagnostic sensitivity and specificity of a filter paper-based agglutination test (FP-DAT) for diagnosis of VL in patients admitted to an upazila health complex in Mymensingh, a VL-endemic region of Bangladesh. The sensitivity of both the conventional direct agglutination test (DAT) and FP-DAT were 100% and 96%, respectively. The specificity of both assays was 100%. However, when the performances of the two assays were compared using McNamar's test, neither the sensitivity nor the specificity of the FP-DAT differed significantly from conventional DAT.

[Development of a novel Francisella tularensis antigen stained with tetrazolium-blue for tularemia microagglutination test]. / Tularemi mikroaglütinasyon testi için tetrazolyum mavisi ile boyali Francisella tularensis antijeninin gelistirilmesi.

The isolation of Francisella tularensis in cultures is the reference method for the laboratory diagnosis of tularemia. However, due to the limitations such as the low sensitivity and need for high safety level and equipped laboratories, serologic methods are frequently used as diagnostic tools. F.tularensis-specific antibodies may be demonstrated by several methods, however microagglutination test (MA) remains the most common method with its high sensitivity and specificity. The aim of this study was to develop a novel MA test antigen prepared from whole F.tularensis cells and stained with tetrazolium-blue for more clear and easier evaluation. F.tularensis NCTC 10857 strain was cultured on the cysteine heart agar supplemented with 9% sheep blood and bacterial cells were harvested by scraping, collected in physiological saline (PS) and centrifuged at 1500 rpm for 10 minutes. For preparing stock antigen suspension cell concentration was adjusted to OD600=1.5, spectrophotometrically. Tetrazolium-blue solution (BTC [3,3'-(3,3'-Dimethoxy[1,1'-biphenyl]-4,4'-diyl) bis [2,5-diphenyl-2H-tetrazolium dichloride], T4375 Sigma-Aldrich) at the final concentration of 1% was added to cell suspension and incubated at 37°C for 5 hours for absorption. Then, the living cells were chemically inactivated by formaldehyde. Repeating centrifugations were performed to discard excess dye and formaline, then 0.4% formaline saline was added on the sediment. Optimum concentration of this novel antigen (BTC-Ag) for MA test was determined by plate titration method by using standard serum sample with a known MA titer (1/128). The performance of BTC-Ag in MA test was evaluated by using 100 patient sera positive for F.tularensis antibodies, and 100 tularemia negative patient sera (of them 50 were seropositive for brucellosis). All of the results were compared with standard MA test in which safranin-O stained antigen (SO-Ag) was used. There was 100% agreement between the two tests performed with BTC-Ag and SO-Ag in tularemia seropositive (in ≥ 1/20 titers and when ±1 dilution variation was accepted as normal) and seronegative sera. No significant cross reactivity with Brucella spp. was observed. Accuracy, sensitivity and specificity of BTC-Ag were found to be 100%. In conclusion, newly developed BTC-Ag for MA test provides better agglutination patterns resulting in a clear supernatant in wells, thus provides easy evaluation for the agglutination reaction, and is expected to facilitate tularemia serodiagnosis.

Exponential error reduction in pretransfusion testing with automation.

BACKGROUND: Protecting the safety of blood transfusion is the top priority of transfusion service laboratories. Pretransfusion testing is a critical element of the entire transfusion process to enhance vein-to-vein safety. Human error associated with manual pretransfusion testing is a cause of transfusion-related mortality and morbidity and most human errors can be eliminated by automated systems. However, the uptake of automation in transfusion services has been slow and many transfusion service laboratories around the world still use manual blood group and antibody screen (G&S) methods. STUDY DESIGN AND METHODS: The goal of this study was to compare error potentials of commonly used manual (e.g., tiles and tubes) versus automated (e.g., ID-GelStation and AutoVue Innova) G&S methods. Routine G&S processes in seven transfusion service laboratories (four with manual and three with automated G&S methods) were analyzed using failure modes and effects analysis to evaluate the corresponding error potentials of each method. RESULTS: Manual methods contained a higher number of process steps ranging from 22 to 39, while automated G&S methods only contained six to eight steps. Corresponding to the number of the process steps that required human interactions, the risk priority number (RPN) of the manual methods ranged from 5304 to 10,976. In contrast, the RPN of the automated methods was between 129 and 436 and also demonstrated a 90% to 98% reduction of the defect opportunities in routine G&S testing. CONCLUSION: This study provided quantitative evidence on how automation could transform pretransfusion testing processes by dramatically reducing error potentials and thus would improve the safety of blood transfusion.

Evaluation of serodiagnostic tests for T.b. gambiense human African trypanosomiasis in southern Sudan.

A survey was conducted in a low-endemic and in a non-endemic area of Sudan to evaluate the specificity and efficiency of different serological antibody detection techniques for Trypanosoma brucei gambiense. Comparisons were made of the card agglutination test for trypanosomiasis (CATT) on diluted blood, on diluted plasma and on eluates from blood dried on filter paper, the LATEX test on diluted plasma and an ELISA on diluted plasma and filter paper. The specificities of all the serological tests were not significantly different from CATT on diluted blood (99.5%). The specificity of CATT on diluted blood was similar (99.3%). The highest sensitivities (100%) were observed with CATT on diluted blood and with CATT and LATEX on diluted plasma. CATT on diluted blood was more cost-efficient than the classic test, CATT on whole blood.

Prevalence of bovine and human brucellosis in western Algeria: comparison of screening tests.

A serological study was carried out in Tiaret province in western Algeria on 1032 cows distributed in 95 flocks to estimate the prevalence of Brucella infection and to compare the sensitivity and specificity of a range of agglutination tests. Screening tests showed 31.5% of herds positive using the buffered plate antigen test and 26.3% using the rose Bengal test compared with 15.7% with the complement fixation test. Using the complement fixation test as the gold standard for confirmatory tests, the Rivanol test was found to be more sensitive but less specific than tube agglutination in detecting brucellosis infection. Three isolates were identified from 105 blood samples from humans with brucellosis and 50 samples of milk and tissues from infected cows and they were all Brucella melitensis biovar 3.

Diagnosing human African trypanosomiasis in Angola using a card agglutination test: observational study of active and passive case finding strategies.

OBJECTIVE: To assess the operational feasibility of detecting human African trypanosomiasis by active and passive case finding using the card agglutination test with serial dilution of serum to guide treatment. SETTING: Trypanosomiasis control programme in the Negage focus, northern Angola, during a period of civil war. DESIGN: Observational study. PARTICIPANTS: 359 patients presenting themselves to health centres with symptoms (passive case finding) and 14,446 people actively screened in villages. MAIN OUTCOME MEASURES: Whole blood and serological tests at different dilutions using the card agglutination test, and detection of parasites by microscopy. RESULTS: Active case finding identified 251 people with a positive card agglutination test result, 10 of whom had confirmed parasites. In those presenting for investigation 34 of 51 with a positive card agglutination test result at the dilution of 1:8 or more used to guide treatment had parasites in blood, lymph node fluid, or cerebrospinal fluid, compared with 10 of 76 in those detected by active case finding: positive predictive values of 67% for passive case detection and 13% for active case detection. Only at a cut-off dilution more than 1:32 was the positive predictive value in active case detection reasonable (46%) and at this dilution 40% of microscopically proved cases were missed. CONCLUSIONS: The card agglutination test is useful for initial screening in active detection of cases with human African trypanosomiasis but, given the toxicity of the drugs, serology using the card agglutination test should be not used alone to guide treatment after active case finding. A second confirmatory test is needed.

Glycolipids of Mycobacterium tuberculosis strain H37Rv are potential serological markers for diagnosis of active tuberculosis.

A simple and cost-effective diagnostic tool (TB Screen Test) for the screening of patients with pulmonary and extrapulmonary tuberculosis and for differentiation of those individuals from individuals without tuberculosis, other common infections, and healthy controls has been developed. The serological responses of purified mycobacterial glycolipid antigens were examined by a liposome agglutination assay. The assay was able to detect very low antiglycolipid antibody concentrations in the infected individuals. The sera from the tuberculosis patient group had significantly higher concentrations of antiglycolipid antibody than the sera from uninfected control subjects, with 94% sensitivity and 98.3% specificity. Glycolipids of Mycobacterium tuberculosis H37Rv antigens were isolated, purified, and characterized. After interchelation with liposome particles, these purified antigens specifically bound to the antiglycolipid antibodies present in the sera of patients with tuberculosis, resulting in the formation of a blue agglutination. This protocol clearly differentiates healthy controls and M. bovis BCG-vaccinated subjects from those with active tuberculosis. The resultant diagnostic tool, the TB Screen Test, is more economical and rapid (4 min) than other currently available products and can be used for the mass screening of a heavily afflicted population.

A discrepancy between cystic echinococcosis confirmed by ultrasound and seropositivity in Turkish children.

In three randomly selected villages of Manisa, Turkey, 630 primary school children were examined for cystic echinococcosis (CE) by a portable ultrasound scanner (US) and chest microfilm. Sera samples of 483 (76.7%) children were tested for anti-E. granulosus antibodies by ELISA and indirect hemagglutination (IHA) tests. Hepatic CE were detected in two cases (0.3%) by US, while 43 (8.9%) and 49 (10.1%) cases were found to be positive for CE by ELISA and IHA, respectively. The high seropositivity levels could have been attributed to extra-abdominal or abortive Echinococcus infections, but probably most of them were false-positives. Due to the discrepancy in results, US should be selected as the primary test in field studies and serologic tests should be performed in all cases with suspected lesions. We could not find any reported community based study on CE in Turkey, in which US was applied; but our results suggest that extensive epidemiological studies are required.

Estratificación de leptospiras por municipios en Villa Clara / Stratification of leptospiras by municipality in Villa Clara province

Se estudiaron 786 sueros pareados de pacientes con sospecha clínica, con evidencia epidemiológica de leptospirosis o sin esta, por la técnica de microaglutinación (MAT), con el objetivo de identificar los serogrupos de mayor reactividad serológica y estratificarlos por municipio. Se obtuvo una positividad de 52,3 por ciento, siendo el serogrupo predominante ballum (11,8 por ciento), seguido de pomona (10,6 por ciento) e icterohaemorragiae (9,7 por ciento). El porcentaje mayor de positividad se observó en los municipios Santo Domingo (30,2 por ciento), Ranchuelo (23,3 por ciento), Encrucijada (12,6 por ciento) y Quemado (11,4 por ciento). La distribución de serogrupos según el municipio mantuvo un resultado similar a la distribución de serogrupos en general, con predominio de ballum en los 3 municipios de mayor número de casos

The effectiveness of active population screening and treatment for sleeping sickness control in the Democratic Republic of Congo.

BACKGROUND: The human African trypanosomiasis (HAT) control programme of the Democratic Republic of Congo (DRC) uses mass screening with the card agglutination test for trypanosomes (CATT). We looked at the contribution of CATT and improved parasitological confirmation to the effectiveness of screening and treatment. METHOD: The effectiveness of the screening and treatment process is measured by the percentage of HAT cases that is effectively cured after a single round of screening. The process is analysed in five steps: (i) the attendance at the screening, (ii) the sensitivity of the screening procedure, (iii) the sensitivity of the parasitological confirmation, (iv) the proportion of the confirmed cases that effectively receive treatment and (v) the cure rate of the treatment. We used a simplified model that multiplies proportions of infected persons that go through each step. We estimated these parameters using a combination of routine data collected by the national control programme over the period January 1997 to December 1998 and published data. For varying attendance rates we compared the effectiveness of screening strategies based on CATT or on CATT combined with improved parasitological confirmation by mini anion exchange column technique (mAECT) with the previously used strategy based on palpation of neck glands and microscopy alone. RESULTS: The model shows that overall effectiveness of the active case detection and treatment strategy is <50% under most scenarios. Attendance rates averaged 74% but showed considerable regional variability and are a major problem in some areas of DRC. The CATT and replacing traditional parasitology by mAECT increases the sensitivity of the screening but a substantial part of the gains are lost at other stages of the screening process. CONCLUSION: Improvements of the HAT screening process such as introduction of CATT or mAECT only make sense if other parameters and attendance rate in particular are optimized at the same time.

A new serum hydatid antigen detection test for diagnosis of cystic echinococcosis.

Cystic echinococcosis (CE) is a major public health problem with a worldwide distribution in both humans and animals. Diagnosis of this disease by simple and rapid immunoassays is a priority. The objective of the present study was to standardize and evaluate the latex agglutination test (LAT) as a simple test for the detection of circulating hydatid antigen in serum. The subjects in this study included 141 patients in the following groups: surgically confirmed CE cases (18), ultrasound-proven cases (26), presumptive CE cases (47), controls with other parasitic disease (25), and healthy controls (25). A polystyrene latex (0.81 microm) suspension was used as a carrier particle for hydatid antibodies in the test. The latex particles were sensitized with hyperimmune hydatid antiserum raised in rabbits. The hydatid antibody-sensitized latex particles were used for the detection of hydatid antigens in serum. The results of the study showed that the LAT could detect the circulating hydatid antigen in 13 (72%) of 18 patients with surgically confirmed CE, 17 (65%) of 26 patients with ultrasound-proven CE, and 19 (40%) of 47 presumptive cases of CE. The test detected antigen in 1 (4%) of 25 controls with other parasitic disease, and no antigen was detected in the serum of 25 healthy controls. The LAT showed a sensitivity of 72%, a specificity of 98%, a positive predictive value of 93%, and a negative predictive value of 91%. The present study is the first report of the LAT for the detection of hydatid antigen in serum in the diagnosis of CE.

Evaluation of the micro-CATT, CATT/Trypanosoma brucei gambiense, and LATEX/T b gambiense methods for serodiagnosis and surveillance of human African trypanosomiasis in West and Central Africa.

OBJECTIVE: To evaluate the performance of serological tests using dried blood on filter-papers (micro-card agglutination test for trypanosomiasis (micro-CATT)) performed under field and laboratory conditions and using whole blood ((CATT/T.b. gambiense) (wb-CATT) and latex agglutination (LATEX/T.b. gambiense) (wb-LATEX)) for the serodiagnosis and surveillance of human African trypanosomiasis in West and Central Africa. METHODS: We evaluated the micro-CATT, wb-CATT and wb-LATEX methods in Côte d'Ivoire and the Central African Republic by screening 940 people. Sensitivity and specificity were calculated for each serological test; only patients with the confirmed presence of trypanosomes in the blood or lymph aspirate were considered true positives. Positive and negative predictive values were also calculated. FINDINGS: Each of the tests showed a lower sensitivity in the Central African Republic than in Côte d'Ivoire. CONCLUSION: The results confirmed the efficiency of the classic wb-CATT to detect sleeping sickness patients. The micro-CATT method can be used for human African trypanosomiasis surveillance if the test is performed on the same day as the blood collection, or if samples are stored at 4 degrees C. Otherwise, micro-CATT can be used when absolute sensitivity is not required. wb-LATEX should only be used for high-specificity screening.

Preliminary evaluation of LATEX/T. b. gambiense and alternative versions of CATT/T. b. gambiense for the serodiagnosis of human african trypanosomiasis of a population at risk in Côte d'Ivoire: considerations for mass-screening.

A study was conducted to compare classical card agglutination test for trypanosomiasis (CATT)/T. b. gambiense with CATT-EDTA and LATEX/T. b. gambiense as alternative field tests for serodiagnosis of Human African Trypanosomiasis. The tests were performed on freshly collected blood in an endemic and a low prevalence area in Côte d'Ivoire. Diagnostic performance of each test was assessed using Quantitative Buffy Coat as the parasitological reference and immune trypanolysis as the serological reference test. According to the parasitological data, CATT-EDTA on 10 microl and LATEX/T. b. gambiense on blood diluted 1:4, detecting all confirmed cases with good specificity (respectively 94.6% and 98.1%) yielded better results than the classical CATT did (one false negative and 92.5% specific). However, when immune trypanolysis data and feasibility are taken into account, the classical CATT remains the test of choice for mass screening under the given field conditions.

Detection of Cryptosporidium parvum antigen by co-agglutination test and ELISA.

Confirmation of the presence of Cryptosporidium in environmental samples is laborious, costly and often difficult. We report here a simple and economic slide agglutination test (co-agglutination test) for detecting cryptosporidial antigen in stool, serum and water. The results show that as a screening method co-agglutination is clearly superior to enzyme-linked immunosorbent assay (ELISA) and modified Ziehl-Neelsen staining, although ELISA is more accurate. The co-agglutination test is recommended for application as a new tool for detecting cryptosporidial antigen in large-scale epidemiological surveys.

A panel of eight tests in the serodiagnosis and immunological evaluation of acute brucellosis.

A panel of eight tests was used to study 200 cases of acute brucellosis, 200 patients negative for brucella as a control group and 200 apparently healthy individuals as a second control group. The best diagnostic test was the rose Bengal test using an imported reagent (BioMérieux, France) and 2 local reagents. This test was improved from being a screening test to be a titrable one. The best two tests used together were the tube agglutination test with Coomb-like test. The indirect fluorescent antibody test had no advantages over the use of other tests. The 2-mercaptoethanol test and C-reactive protein test were useful in checking the brucellosis activity. Normal numbers of E-rosette forming cells and inefficient neutrophils in phagocytosis were found in peripheral blood during acute brucellosis.

Evaluation of a standardized direct agglutination test (DAT) for the diagnosis of visceral leishmaniasis in Kenya.

A prototype test kit being developed, by the World Health Organization (WHO), for the diagnosis of visceral leishmaniasis (VL) was evaluated in the Baringo district of Rift Valley province in Kenya. The screening of approximately 10,000 individuals for the signs of VL produced 305 suspected cases. These cases and 304 controls matched for sex and age (+/- 2 years) were then tested with the kit, which is based on a direct agglutination test (DAT). The evaluation was a three-stage process. The first stage, the field screening, involved screening filter-paper samples of dried blood from the suspects and controls at a DAT titre of 1:500. The second stage, the laboratory titration, involved screening of the same individuals by testing freshly eluted filter-paper samples at 1:500 to 1:2000 dilution. In the third stage, the full-scale titration, all samples that had been positive at 1:2000 were titrated at 1:500-1:512,000. All the suspects giving DAT titres of 1:2000 or higher were considered positive for VL. This diagnosis was checked, whenever possible, by the examination of smears and/or cultures of splenic aspirates for leishmanial parasites. Those found to be parasitologically positive were put on a standard treatment regime of 20 mg sodium stibogluconate (Pentostam)/kg.day. Although 42 (13.8%) of the 305 clinical suspects investigated were DAT-positive (at 1:2000), it was only possible to take splenic aspirates from 32. Four (12.5%) of these 32 were apparently false-positives by DAT, as no parasites could be detected in their splenic aspirates. The others provided positive smears and cultures (27 cases) or a negative smear but a positive culture (one case). It was possible to re-examine two of the four serologically positive but parasitologically negative VL suspects at a 3-month follow-up: neither had a palpable spleen, one had seroconverted and the other had much lower DAT titre (1:32,000) than when investigated previously (1:128,000). All the parasitologically confirmed cases remained DAT-positive (1:2000) at this follow-up. The low cut-off titre (1:2000) and the simple procedure should make the kit suitable for use by health workers at all levels of primary-health care, including those with limited training and skills, for screening rural communities at risk of VL.

Agglutinins for brucellae antigens in blood sera of an urban and rural population in Kenya.

The antibody titres for Brucella arbotus and Br. melitensis in 364 sera from healthy individuals in Nairobi and Naivasha are presented. A majority (96%) had no detectable agglutinins. Reactivity was markedly higher in the Naivasha serum samples, than in those from Nairobi. In Naivasha, seven per cent showed reactivity, whereas in Nairobi a larger majority (98%), showed no reactivity, with antibody titres ranging from 1:20-1:160. Age and sex were found to have no effect on antibody titre distribution in the two populations. The presence of brucellae antibodies in the healthy population screened (with titres upto 1:80) may be due to exposure to brucellae antigens, rather than denoting brucellosis, this titre could therefore be taken as the baseline in the healthy Kenyan population.