Estimating epidemiological parameters using diagnostic testing data from low pathogenicity avian influenza infected turkey houses

Abstract

Limiting spread of low pathogenicity avian influenza (LPAI) during an outbreak is critical to reduce the negative impact on poultry producers and local economies. Mathematical models of disease transmission can support outbreak control efforts by estimating relevant epidemiological parameters. In this article, diagnostic testing data from each house on a premises infected during a LPAI H5N2 outbreak in the state of Minnesota in the United States in 2018 was used to estimate the time of virus introduction and adequate contact rate, which determines the rate of disease spread. A well-defined most likely time of virus introduction, and upper and lower 95% credibility intervals were estimated for each house. The length of the 95% credibility intervals ranged from 11 to 22 with a mean of 17 days. In some houses the contact rate estimates were also well-defined; however, the estimated upper 95% credibility interval bound for the contact rate was occasionally dependent on the upper bound of the prior distribution. The estimated modes ranged from 0.5 to 6.0 with a mean of 2.8 contacts per day. These estimates can be improved with early detection, increased testing of monitored premises, and combining the results of multiple barns that possess similar production systems.

A systematic review of mechanistic models used to study avian influenza virus transmission and control

“…Most of the PBMs presented in the review (16/27; Table 2 ) defined individual birds as the epidemiological unit. Seven studied the transmission dynamics between individual birds and humans [ 44 , 45 , 52 , 58 , 78 – 80 ], eight between individual birds in a farm [ 35 , 57 , 62 , 64 , 65 , 73 , 76 , 77 ], and one between domestic birds and wild birds [ 66 ]. The other PBMs (11/27; Table 2 ) studied transmission between poultry farms [ 39 , 41 , 43 , 48 , 68 , 69 , 72 ] or transmission between poultry populations pooled at the administrative unit level [ 37 , 49 , 51 , 53 ].…”

Simulated Flock-Level Shedding Characteristics of Turkeys in Ten Thousand Bird Houses Infected with H7 Low Pathogenicity Avian Influenza Virus Strains

“…The virus shedding model has several potential applications for informing risk management during an LPAI outbreak. For example, the Ct component could improve estimates for the time of virus introduction from diagnostic test results, especially when few results are available [12]. Nickbakhsh et al (2013) included a transmission term in their within flock HPAI transmission model for spread due to susceptible bird contacts with infectious fecal contaminated dust or equipment [47].…”

“…Specific methodology and parameterization of the compartmental component was implemented as described in [12]. The outbreak was assumed to begin with a single latently infected bird.…”

“…The proportion of turkeys that seroconvert was set to 99% based on the results of Spackman et al (2010) [8]. The adequate contact rate for a simulation iteration was drawn from a uniform distribution with minimum 0.5, and maximum 4.0, based on the results of Bonney et al (2021) [12]. A summary of the transmission model parameters is given in Table 1.…”

“…Adequate contact rate, the parameter that determines the rate of disease transmission ~Uniform (min = 0.5, max = 4.0) [12] Latent period length distribution ~Gamma (shape = 2.58, scale = 0.24); mean = 0.63 days, standard deviation = 0.39 days [9,14,15] Infectious period length distribution ~Gamma (shape = 4.04, scale = 2.92); mean = 11.78 days, standard deviation = 5.86 days [8,9,[13][14][15][16] Time from infection to seroconversion distribution ~Gamma (shape = 3.56, scale = 1.63); mean = 5.80 days, standard deviation = 3.07 days [17][18][19][20] Proportion of infected birds that die 0.01 [12] Proportion of infected birds that seroconvert 0.99 [8]…”