Influence of Human Behavior on COVID-19 Dynamics Based on a Reaction-Diffusion Model.

To investigate the influence of human behavior on the spread of COVID-19, we propose a reaction-diffusion model that incorporates contact rate functions related to human behavior. The basic reproduction number R0 is derived and a threshold-type result on its global dynamics in terms of R0 is established. More precisely, we show that the disease-free equilibrium is globally asymptotically stable if R0≤1; while there exists a positive stationary solution and the disease is uniformly persistent if R0>1. By the numerical simulations of the analytic results, we find that human behavior changes may lower infection levels and reduce the number of exposed and infected humans.

Selective and stable elimination of endosymbionts from multiple-infected whitefly Bemisia tabaci by feeding on a cotton plant cultured in antibiotic solutions.

The maternally heritable endosymbiont provides many ecosystem functions. Antibiotic elimination of a specific symbiont and establishment of experimental host lines lacking certain symbionts enable the roles of a given symbiont to be explored. The whitefly Bemisia tabaci (Gennadius) in China harbors obligate symbiont Portiera infecting each individual, as well as facultative symbionts, such as Hamiltonella, Rickettsia and Cardinium, with co-infections occurring relatively frequently. So far no studies have evaluated the selectivity and efficacy of a specific symbiont elimination using antibiotics in whiteflies co-infected with different symbionts. Furthermore, no success has been achieved in establishing certain symbiont-free B. tabaci lines. In this study, we treated Hamiltonella-infected B. tabaci line, Hamiltonella-Rickettsia-co-infected line and Hamiltonella-Cardinium co-infected line by feeding B. tabaci adults with cotton plants cultured in water containing rifampicin, ampicillin or a mixture of them, aiming to selectively curing symbiont infections and establishing stable symbiont-free lines. We found ampicillin selectively eliminated Cardinium without affecting Portiera, Hamiltonella and Rickettsia, although they coexisted in the same host body. Meanwhile, all of the symbionts considered in our study can be removed by rifampicin. The reduction of facultative symbionts occurred at a much quicker pace than obligate symbiont Portiera during rifampicin treatment. Also, we measured the stability of symbiont elimination in whitefly successive generations and established Rickettsia-infected and Cardinium-infected lines which are absent in natural populations. Our results provide new protocols for selective elimination of symbionts co-existing in a host and establishment of different symbiont-infected host lines.

Percutaneous transhepatic biliary stenting in patients with intradiverticular papillae and biliary strictures caused by ampullary carcinoma: A case report.

Endoscopic retrograde cholangiopancreatography with endoscopic sphincterotomy is a well-established procedure for the treatment of bile duct strictures. However, the procedure is difficult to perform in patients with intradiverticular papillae or tumor infiltration of the major papilla. Percutaneous transhepatic biliary stenting (PTBS) is commonly used in the management of malignant biliary stricture. The current study reports two cases of PTBS performed to treat malignant obstructive jaundice caused by ampullary carcinoma complicated with intradiverticular papillae. PTBS is potentially a safe technique for this relatively rare condition.

[Minimum dose of Trichinella spiralis muscle larvae to infect mice].

Seventy male mice (Kunming strain) were randomly divided into 7 groups (10 mice per group), each mouse was orally inoculated with 30, 25, 20, 15, 10, 5 or 3 muscle stage larvae of Trichinella spiralis, respectively. All infected mice were sacrificed 6 weeks post-inoculation, number of larvae per gram (LPG) of diaphragm were counted by compression method (trichinelloscopy), the carcass was digested by artificial digestion method and LPG was counted. The larval detection rate by trichinelloscopy and digestion method was 100% (10/10) in all mice infected with 30, 25, 20, 15 or 10 larvae, but 70% (7/10) and 100% in mice infected with 5 larvae, respectively. No larva was found by either method in mice infected with 3 larvae. There is a positive correlation between the larval burden (of diaphragm and muscle) and the infecting dose (r = 0.759, P < 0.05; r = 0.638, P < 0.05), and the minimum infection dose to a mouse is 5 larvae.

[Identification of six Trichinella isolates from China by multiplex PCR].

OBJECTIVE: To identify and classify six isolates of swine-originated Trichinella from China. METHODS: Five specific pairs of primers were synthesized based on DNA sequence of expansion segment V region and internal transcribed spacers (ITS1 and ITS2) of ribosomal DNA repeat from Trichinella. International reference strains of five Trichinella species [Trichinella spiralis (T1), T. nativa (T2), T. britovi (T3), T. pseudospiralis (T4) and T. nelsoni (T7)] were used as control. Six swine Trichinella isolates from Henan, Yunnan, Harbin, Tongjiang of Heilongjiang, Hubei and Tianjin were identified by multiplex PCR and its effecting factors of PCR amplification were observed. RESULTS: Electrophoresis results of multiplex PCR products of Trichinella larvae showed that the band (173 bp) of the six isolates was the same as T. spiralis (T1). The specific band (173 bp) was detected by multiplex PCR through amplification from issues of single T. spiralis larva, the larvae conserved in 80% ethanol for 6 months, the larvae stored in 10% formaldehyde, in 0.05% formaldehyde, 0.2% sodium azide or 0.05% merthiotate for 2 weeks, or fresh mouse muscle with larvae. CONCLUSION: All the six swine Trichinella isolates are identified as T. spiralis (T1) by multiplex PCR.

[Effects of applying Sophora alopecuroids extracts and emamectin on the growth, development, and fecundity of diamondback moth plutella xylostella].

In this paper, the methanol- and water extracts of Sophora alopecuroids were applied respectively with emamectin, to study their effects on the growth, development, and fecundity of diamondback moth Plutella xylostella. The results showed that the oral toxicity of the mixtures to the 3rd larvae of P. xylostella was much higher than that of emamectin, with the medium lethal concentration (LC50) of methanol extract plus emamectin, water extract plus emamectin, and emamectin being 0.19, 0.32 and 0.51 mg L(-1), respectively. The pupated percentage, emergence percentage, and fecundity of P. xylotella were obviously negatively affected after treated the 3rd larvae with sub-lethal dosage of the mixtures and emamectin.