43 research outputs found
The variable prevalence of bovine tuberculosis among dairy herds in Central Ethiopia provides opportunities for targeted intervention.
Bovine tuberculosis (bTB) is an important disease for dairy productivity, as well as having the potential for zoonotic transmission. Previous prevalence studies of bTB in the dairy sector in central Ethiopia have suggested high prevalence, however, they have been limited to relatively small scale surveys, raising concerns about their representativeness. Here we carried out a cross sectional one-stage cluster sampling survey taking the dairy herd as a cluster to estimate the prevalence of bTB in dairy farms in six areas of central Ethiopia. The survey, which to date is by far the largest in the area in terms of the number of dairy farms, study areas and risk factors explored, took place from March 2016 to May 2017. This study combined tuberculin skin testing and the collection of additional herd and animal level data by questionnaire to identify potential risk factors contributing to bTB transmission. We applied the single intradermal cervical comparative tuberculin (SICCT) test using >4mm cut-off for considering an individual animal as positive for bTB; at least one reactor animal was required for a herd to be considered bTB positive. Two hundred ninety-nine dairy herds in the six study areas were randomly selected, from which 5,675 cattle were tested. The overall prevalence of bTB after standardisation for herd-size in the population was 54.4% (95% CI 48.7-60%) at the herd level, and it was 24.5% (95% CI 23.3-25.8) at the individual animal level. A Generalized Linear Mixed Model (GLMM) with herd and area as random effect was used to explore risk factors association with bTB status. We found that herd size, age, bTB history at farm, and breed were significant risk factors for animals to be SICCT positive. Animals from large herds had 8.3 times the odds of being tuberculin reactor (OR: 8.3, p-value:0.008) as compared to animals from small herds. The effect of age was strongest for animals 8-10 years of age (the oldest category) having 8.9 times the odds of being tuberculin reactors (OR: 8.9, p-value:<0.001) compared to the youngest category. The other identified significant risk factors were bTB history at farm (OR: 5.2, p-value:0.003) and cattle breed (OR: 2.5, p-value: 0.032). Our study demonstrates a high prevalence of bTB in central Ethiopia but with a large variation in within-herd prevalence between herds, findings that lays an important foundation for the future development of control strategies
Identification of novel Coxiella burnetii genotypes from Ethiopian ticks
Background:
Coxiella burnetii
, the etiologic agent of Q fever, is a highly infectious
zoonotic bacterium. Genetic information about the strains of this worldwide
distributed agent circulating on the African continent is limited. The aim of the
present study was the genetic characterization of
C. burnetii
DNA samples
detected in ticks collected from Ethiopian cattle and their comparison with other
genotypes found previously in other parts of the world.
Methodology/Principal Findings:
A total of 296 tick samples were screened by
real-time PCR targeting the IS
1111
region of
C. burnetii
genome and from the 32
positive samples, 8 cases with sufficient
C. burnetii
DNA load (
Amblyomma
cohaerens
,n
5
6;
A. variegatum
,n
5
2) were characterized by multispacer sequence
typing (MST) and multiple-locus variable-number tandem repeat analysis (MLVA).
One novel sequence type (ST), the proposed ST52, was identified by MST. The
MLVA-6 discriminated the proposed ST52 into two newly identified MLVA
genotypes: type 24 or AH was detected in both
Amblyomma
species while type 26
or AI was found only in
A. cohaerens
.
Conclusions/Significance:
Both the MST and MLVA genotypes of the present
work are closely related to previously described genotypes found primarily in cattle
samples from different parts of the globe. This finding is congruent with the source
hosts of the analyzed Ethiopian ticks, as these were also collected from cattle. The
present study provides genotype information of
C. burnetii
from this seldom studied
East-African region as well as further evidence for the presumed host-specific
adaptation of this agent
Mycobacterium tuberculosis causing tuberculous lymphadenitis in Maputo, Mozambique
BACKGROUND:
The zoonosis bovine tuberculosis (TB) is known to be responsible for a considerable proportion of extrapulmonary TB. In Mozambique, bovine TB is a recognised problem in cattle, but little has been done to evaluate how Mycobacterium bovis has contributed to human TB. We here explore the public health risk for bovine TB in Maputo, by characterizing the isolates from tuberculous lymphadenitis (TBLN) cases, a common manifestation of bovine TB in humans, in the Pathology Service of Maputo Central Hospital, in Mozambique, during one year.
RESULTS:
Among 110 patients suspected of having TBLN, 49 had a positive culture result. Of those, 48 (98 %) were positive for Mycobacterium tuberculosis complex and one for nontuberculous mycobacteria. Of the 45 isolates analysed by spoligotyping and Mycobacterial Interspersed Repetitive Unit - Variable Number Tandem Repeat (MIRU-VNTR), all were M. tuberculosis. No M. bovis was found. Cervical TBLN, corresponding to 39 (86.7 %) cases, was the main cause of TBLN and 66.7 % of those where from HIV positive patients. We found that TBLN in Maputo was caused by a variety of M. tuberculosis strains. The most prevalent lineage was the EAI (n?=?19; 43.2 %). Particular common spoligotypes were SIT 48 (EAI1_SOM sublineage), SIT 42 (LAM 9), SIT 1 (Beijing) and SIT53 (T1), similar to findings among pulmonary cases.
CONCLUSIONS:
M. tuberculosis was the main etiological agent of TBLN in Maputo. M. tuberculosis genotypes were similar to the ones causing pulmonary TB, suggesting that in Maputo, cases of TBLN arise from the same source as pulmonary TB, rather than from an external zoonotic source. Further research is needed on other forms of extrapulmonary TB and in rural areas where there is high prevalence of bovine TB in cattle, to evaluate the risk of transmission of M. bovis from cattle to humans.Swedish International Development Cooperation Agency / Department for Research Cooperation (Sida/SAREC) through Eduardo Mondlane University and Karolinska Institutet Research and Training (KIRT) collaboratio
TwoâStage Polyelectrolyte Assembly Orchestrated by a Clock Reaction
Controlling the transient selfâassembly of (macro)molecular building blocks is of fundamental interest, both to understand the dynamic processes occurring in living systems and to develop new generations of functional materials. The subtle interplay between different types of physicochemical interactions, as well as the possible reaction pathways, are crucial when both thermodynamic and kinetic factors play substantial roles, as in the case of transient supramolecular assemblies. Clock reactions are a promising tool to achieve temporal control over selfâassembly in nonâliving materials. Here, we report on the tunable association of poly(allylamine hydrochloride) (PAH) fueled by the formaldehydeâsulfite clock reaction. The electrostatic interaction between the large macromolecules and the small, oppositely charged sulfite ions gives rise to micronâsized coacervateâlike complexes. As the clock proceeds, sulfite is completely depleted and the complexes dissociate. However, under suitable conditions, a subsequent reaction between the polyelectrolyte and formaldehyde can lockâin the preformed supramolecular structure, giving rise to covalently crosslinked colloidal particles
Controlling the Formation of Polyelectrolyte Complex Nanoparticles Using Programmable pH Reactions
Enabling complexation of weak polyelectrolytes, in the presence of a programmable pH-modulation, offers a means to achieve temporal control over polyelectrolyte coassembly. Here, by mixing oppositely charged poly(allylamine hydrochloride) and poly(sodium methacrylate) in a (bi)sulfite buffer, nanoscopic complex coacervates are formed. Addition of formaldehyde initiates the formaldehyde-sulfite clock reaction, affecting the polyelectrolyte assembly in two ways. First, the abrupt pH increase from the reaction changes the charge density of the polyelectrolytes and thus the ratio of cationic and anionic species. Simultaneously, reactions between the polyamine and formaldehyde lead to chemical modifications on the polymer. Interestingly, coreâshell polymeric nanoparticles are produced, which remain colloidally stable for months. Contrastingly, in the same system, in the absence of the clock reaction, aggregation and phase separation occur within minutes to days after mixing. Introducing an acid-producing reaction enables further temporal control over the coassembly, generating transient nanoparticles with nanoscopic dimensions and an adjustable lifetime of tens of minutes
Impact of poly(ethylene glycol) functionalized lipids on ordering and fluidity of colloid supported lipid bilayers
Colloid supported lipid bilayers (CSLBs) are highly appealing building blocks for functional colloids. In this contribution, we critically evaluate the impact on lipid ordering and CSLB fluidity of inserted additives. We focus on poly(ethylene glycol) (PEG) bearing lipids, which are commonly introduced to promote colloidal stability. We investigate whether their effect on the CSLB is related to the incorporated amount and chemical nature of the lipid anchor. To this end, CSLBs were prepared from lipids with a low or high melting temperature (Tm), DOPC, and DPPC, respectively. Samples were supplemented with either 0, 5 or 10 mol% of either a low or high Tm PEGylated lipid, DOPE-PEG2000 or DSPE-PEG2000, respectively. Lipid ordering was probed via differential scanning calorimetry and fluidity by fluorescence recovery after photobleaching. We find that up to 5 mol% of either PEGylated lipids could be incorporated into both membranes without any pronounced effects. However, the fluorescence recovery of the liquid-like DOPC membrane was markedly decelerated upon incorporating 10 mol% of either PEGylated lipids, whilst insertion of the anchoring lipids (DOPE and DSPE without PEG2000) had no detectable impact. Therefore, we conclude that the amount of incorporated PEG stabilizer, not the chemical nature of the lipid anchor, should be tuned carefully to achieve sufficient colloidal stability without compromising the membrane dynamics. These findings offer guidance for the experimental design of studies using CSLBs, such as those focusing on the consequences of intra- and inter-particle inhomogeneities for multivalent binding and the impact of additive mobility on superselectivity. Graphical abstract: Impact of poly(ethylene glycol) functionalized lipids on ordering and fluidity of colloid supported lipid bilayer
Temperature simulation and its application to steel quality control in bar rolling
46.50; Translated from Japanese (Kobe Res. Dev. 1987 v. 37(4) p. 19-22)Available from British Library Document Supply Centre- DSC:9022.06(BISI-Trans--26558)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo