For infectious diseases, the transmission capacity of disease-inducing parasites is one of the key traits determining the extent and rate of disease incidence. In the pine wilt disease system, the pinewood nematode Bursaphelenchus xylophilus (Steiner et Buhrer) (Nematoda: Aphelenchoididae) is transmitted to healthy pine trees by cerambycid beetle adults of the genus Monochamus, causing rapid wilting. To express the nematode transmission capacity, we proposed the probability (q) of a nematode being transmitted to trees by a beetle individual and the nematode transmission probability (Q) by a beetle population. The q value was calculated as nt/ni, where ni was the initial number of nematodes that a beetle carried and nt was the number of nematodes transmitted by it. The Q value was calculated as the proportion of nematodes transmitted by a beetle population and estimated using the ni–q relation and the frequency distribution of ni. Application of nematode transmission probabilities indicated that the q value decreased with increasing ni value and that the negative slope of regression line of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">${\text{arcsin}}\sqrt q$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>arcsin</mtext> <msqrt> <mi>q</mi> </msqrt> </mrow> </math></EquationSource> </InlineEquation> on <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${\text{log}}_{10} n_{i}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mtext>log</mtext> <mn>10</mn> </msub> <msub> <mi>n</mi> <mi>i</mi> </msub> </mrow> </math></EquationSource> </InlineEquation> was steeper for the B. xylophilus–M. alternatus Hope (Coleoptera: Cerambycidae) and B. xylophilus–M. carolinensis systems than for the B. mucronatus–M. saltuarius system. The Q value was greatest for the system containing M. alternatus and lowest for the system containing M. carolinensis. Those transmission probabilities would help to deeply understand the transmission biology of B. xylophilus.

A novel method for estimating the transmission capacity of Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae)

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发表日期：

2025年11月8日

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Katsumi Togashi,
Shota Jikumaru

摘要

For infectious diseases, the transmission capacity of disease-inducing parasites is one of the key traits determining the extent and rate of disease incidence. In the pine wilt disease system, the pinewood nematode Bursaphelenchus xylophilus (Steiner et Buhrer) (Nematoda: Aphelenchoididae) is transmitted to healthy pine trees by cerambycid beetle adults of the genus Monochamus, causing rapid wilting. To express the nematode transmission capacity, we proposed the probability (q) of a nematode being transmitted to trees by a beetle individual and the nematode transmission probability (Q) by a beetle population. The q value was calculated as n_t/n_i, where n_i was the initial number of nematodes that a beetle carried and n_t was the number of nematodes transmitted by it. The Q value was calculated as the proportion of nematodes transmitted by a beetle population and estimated using the n_i–q relation and the frequency distribution of n_i. Application of nematode transmission probabilities indicated that the q value decreased with increasing n_i value and that the negative slope of regression line of ${\text{arcsin}}\sqrt q$ $arcsin \sqrt{q}$ on ${\text{log}}_{10} n_{i}$ ${log}_{10} n_{i}$ was steeper for the B. xylophilus–M. alternatus Hope (Coleoptera: Cerambycidae) and B. xylophilus–M. carolinensis systems than for the B. mucronatus–M. saltuarius system. The Q value was greatest for the system containing M. alternatus and lowest for the system containing M. carolinensis. Those transmission probabilities would help to deeply understand the transmission biology of B. xylophilus.