1·Sewage and sludge are a kind of organic fertilizer that is rich in organic matter, nitrogen and other microelements, and it also contains pathogeny microbes and parasitic ovum etc.
城市污泥是一种富含有机质、高氮、高磷及多种微量元素的有机肥，并含有病原微生物、寄生虫卵等。
2·Indirect harm Cockroach carries a variety of pathogenic microorganisms such as bacteria, virus, protozoon, parasitic ovum and fungi, etc.
蟑螂能携带多种细菌、病毒、原虫、寄生虫卵、真菌等病原微生物。