Dogs on the move: Estimating the risk of rabies in imported dogs in the United States, 2015-2022

BACKGROUND

Dog-mediated rabies virus variant (DMRVV), a zoonotic pathogen that causes a deadly disease in animals and humans, is present in more than 100 countries worldwide but has been eliminated from the United States since 2007. In the United States, the U.S. Centers for Disease Control and Prevention has recorded four instances of rabies in dogs imported from DMRVV-enzootic countries since 2015. However, it remains uncertain whether the incidence of DMRVV among imported dogs from these countries significantly surpasses that of domestically acquired variants among domestic U.S. dogs.

AIM

This evaluation aimed to estimate the number of dogs imported from DMRVV-enzootic countries and compare the risk of rabies between imported dogs and the U.S. domestic dog population.

MATERIALS AND METHODS

Data from the CDC's dog import permit system (implemented during 2021 under a temporary suspension of dog importation from DMRVV-enzootic countries) and U.S. Customs and Border Protection's Automated Commercial Environment system, each of which records a segment of dogs entering the U.S. from DMRVV-enzootic countries, was analysed. Additionally, we estimated the incidence rate of rabies in dogs imported from DMRVV-enzootic countries and compared it to the incidence rate within the general U.S. dog population, due to domestically acquired rabies variants, over the eight-year period (2015-2022).

RESULTS

An estimated 72,589 (range, 62,660-86,258) dogs were imported into the United States annually between 2015 and 2022 from DMRVV-enzootic countries. The estimated incidence rate of rabies was 16 times higher (range, 13.2-19.4) in dogs imported from DMRVV-enzootic countries than that estimated for domestically acquired rabies in the general U.S. dog population.

CONCLUSIONS

Preventing human exposure to dogs with DMRVV is a public health priority. The higher risk of rabies in dogs imported from DMRVV-enzootic countries supports the need for importation requirements aimed at preventing the reintroduction of DMRVV into the United States.

Plasma concentrations of apolipoprotein B are modulated by a gene--diet interaction effect between the LFABP T94A polymorphism and dietary fat intake in French-Canadian men

Hyperapobetalipoproteinemia is a common feature of the metabolic syndrome and could result from the interaction between genetic and dietary factors. The objective of this study was to verify whether dietary fat intake interacts with the T94A polymorphism of the liver fatty acid-binding protein (LFABP) gene to modulate plasma apolipoprotein (apo) B levels. Dietary fat and saturated fat intakes were obtained by a dietitian-administered food frequency questionnaire and the LFABP T94A genotype was determined by a PCR-RFLP based method in 623 French-Canadian men recruited through the Chicoutimi Lipid Clinic (279 T94/T94, 285 T94/A94, and 59 A94/A94). The LFABP T94A polymorphism was not associated with plasma apo B levels when fat intake was not taken into consideration. However, in a model including the polymorphism, fat intake expressed as a percentage of total energy intake, the interaction term and covariates, the variance in apo B concentrations was partly explained by the LFABP T94A polymorphism (5.24%, p = 0.01) and by the LFABP T94A*fat interaction (6.25%, p = 0.005). Results were similar when saturated fat replaced fat intake in the model (4.49%, p = 0.02 for LFABP T94A and 6.43%, p = 0.004 for the interaction). Moreover, in men consuming more than 30% of energy from fat, the odds ratio for having plasma apo B levels above 1.04 g/L for A94 carriers was of 0.40 (p = 0.02) compared to T94/T94 homozygotes. Results were similar for carriers of the A94 allele consuming more than 10% of energy from saturated fat (OR: 0.32, p = 0.005). In conclusion, T94/T94 exhibit higher apo B levels whereas carriers of the A94 allele seem to be protected against high apo B levels when consuming a high fat and saturated fat diet. These findings reinforce the importance to take into account gene-diet interactions in the prevention and management of the metabolic syndrome.

Stabilization of active-site loops in NH3-dependent NAD+ synthetase from Bacillus subtilis

The NH(3)-dependent NAD(+) synthetase (NADS) participates in the biosynthesis of nicotinamide adenine dinucleotide (NAD(+)) by transforming nicotinic acid adenine dinucleotide (NaAD) to NAD(+). The structural behavior of the active site, including stabilization of flexible loops 82-87 and 204-225, has been studied by determination of the crystal structures of complexes of NADS with natural substrates and a substrate analog. Both loops are stabilized independently of NaAD and solely from the ATP-binding site. Analysis of the binding contacts suggests that the minor loop 82-87 is stabilized primarily by a hydrogen bond with the adenine base of ATP. Formation of a coordination complex with Mg(2+) in the ATP-binding site may contribute to the stabilization of the major loop 204-225. The major loop has a role in substrate recognition and stabilization, in addition to the protection of the reaction intermediate described previously. A second and novel Mg(2+) position has been observed closer to the NaAD-binding site in the structure crystallized at pH 7.5, where the enzyme is active. This could therefore be the catalytically active Mg(2+).

Thermal stabilities of mutant Escherichia coli tryptophan synthase alpha subunits

Random chemical mutagenesis, in vitro, of the 5' portion of the Escherichia coli trpA gene has yielded 66 mutant alpha subunits containing single amino acid substitutions at 49 different residue sites within the first 121 residues of the protein; this portion of the alpha subunit contains four of the eight alpha helices and three of the eight beta strands in the protein. Sixty-two of the subunits were examined for their heat stabilities by sensitivity to enzymatic inactivation (52 degrees C for 20 min) in crude extracts and by differential scanning calorimetry (DSC) with 29 purified proteins. The enzymatic activities of mutant alpha subunits that contained amino acid substitutions within the alpha and beta secondary structures were more heat labile than the wild-type alpha subunit. Alterations only in three regions, at or immediately C-terminal to the first three beta strands, were stability neutral or stability enhancing with respect to enzymatic inactivation. Enzymatic thermal inactivation appears to be correlated with the relative accessibility of the substituted residues; stability-neutral mutations are found at accessible residual sites, stability-enhancing mutations at buried sites. DSC analyses showed a similar pattern of stabilization/destabilization as indicated by inactivation studies. Tm differences from the wild-type alpha subunit varied +/- 7.6 degrees C. Eighteen mutant proteins containing alterations in helical and sheet structures had Tm's significantly lower (-1.6 to -7.5 degrees C) than the wild-type Tm (59.5 degrees C). In contrast, 6 mutant alpha subunits with alterations in the regions following beta strands 1 and 3 had increased Tm's (+1.4 to +7.6 degrees C). Because of incomplete thermal reversibilities for many of the mutant alpha subunits, most likely due to identifiable aggregated forms in the unfolded state, reliable differences in thermodynamic stability parameters are not possible. The availability of this group of mutant alpha subunits which clearly contain structural alterations should prove useful in defining the roles of certain residues or sequences in the unfolding/folding pathway for this protein when examined by urea/guaninidine denaturation kinetic analysis.