FabAV antivenin use after copperhead snakebite: clinically indicated or knee-jerk reaction?

Crotalidae Polyvalent Immune Fab (Ovine) (FabAV) antivenin is commonly recommended after pit viper snakebites. Because copperhead envenomations are usually self-limited, some physicians are reluctant to use this costly treatment routinely, while others follow a more liberal approach. We hypothesized that, in practice, only patients with evidence of significant (moderate or severe) copperhead envenomation [those with snakebite severity score (SSS) > 3] receive FabAV and examined a large cohort to determine the relationship between clinical findings and FabAV administration. Methods All data from patients evaluated for copperhead snakebite at a rural tertiary referral center from 5/2002 to 10/2013 were compiled. Demographics, transfer status, antivenin use, and clinical findings were collected; SSS was calculated. The relationships among FabAV use, clinical findings, and SSS were analyzed using t-test, chi-square, and Pearsons coefficient (p 0.05 was significant). Results During the study period, 318 patients were treated for copperhead snakebite; 44 (13.8 %) received antivenin. Median dose was four vials (range: 110; IQR: 4,6). There were no deaths. Most patients receiving FabAV (63.6 %) were admitted. With regard to demographics and symptoms, only the degree of swelling (moderate vs. none/mild; p 0.01) and bite location (hand/arm vs. leg: p 0.0001) were associated with FabAV use. A SSS > 3, indicating moderate or severe envenomation, was only very weakly correlated with antivenin use (r = 0.217;p 0.0001). The majority of patients with SSS > 3 (65.8 %) did not receive antivenin while most patients who did receive antivenin (70.5 %) had SSS 3 (indicating mild envenomation). Conclusions Considerable variation occurs in antivenin administration after copperhead snakebite. Use of FabAV appears poorly correlated with patients symptoms. This practice may expose patients to the risks of antivenin and increasing costs of medical care without improving outcomes. Guidelines used for treating other pit viper strikes, such as rattlesnake or cottonmouth snakebite may be too liberal for copperhead envenomations. Our data suggests that most patients with mild or moderate envenomation appear to do well independent of FabAV use. We suggest, for patients with copperhead snakebite, that consideration be given to withholding FabAV for those without clinical evidence of severe envenomation until prospective randomized data are available.

Molecular identification and sequence analysis of broad bean wilt virus 2 isolates from atractylodes macrocephala Koidz / 病毒学报

To identity the pathogen that causes the mosaic and yellowing symptoms on Atractylodes macrocephala Koidz in Jiangxian, Shanxi province, biological inoculation, sequence-independent amplification (SIA),RT-PCR and other identification methods were used. The results showed that the chlorotic and necrosis symptoms occurred in the indicator plant Chenopodium quinoa after it was infected with the pathogen,and the same symptoms appeared after the reinoculation of healthy Atractylodes macrocephala Koidz; this reflected that the disease was likely to be caused by a virus. The results of SIA and sequencing showed that Broad bean wilt virus 2 (BBWV2) was present in severely mosaic Atractylodes macrocephala Koidz leaves. To further characterize the BBWV2 isolate from Atractylodes macrocephala (BBWV2-Am), the polyprotein partial gene encoded by BBWV2-Am RNA2 was cloned and sequenced. Sequence alignments showed that the nucleotide sequence identity of BBWV2-Am SCP and LCP genes ranged from 79.3% to 87.2% and from 80.1% to 89.2% compared to other BBWV2 strains,respectively; the deduced amino acid sequence similarities of the two gene products ranged from 91.2% to 95.7% and from 89.44 to 95.5%, respectively,compared to those of other BBWV2 strains. Phylogenetic comparisons showed that BBWV2-Am was most likely to be related to BBWV2-Rg,but formed an independent branch. This is the first report of BBWV2 in Atractylodes macrocephala Koidz.