**6. Geographic regions where resistance has developed**

Initially, the development of resistance against nematicidal drugs was reported in the Southern hemisphere, and the most resistant was studied on *H*. *contortus*


**Table 2.**

*Geographical distribution of anthelmintic resistance developed by helminths in different parts of the world (selected references).*

*Anthelmintic Drug Resistance in Livestock: Current Understanding and Future Trends DOI: http://dx.doi.org/10.5772/intechopen.104186*

nematode. The development of resistance has differed geographically based on various factors such as weather conditions, species of parasite, mode of therapy, use of variable drugs, etc. The resistance rate is slightly lower in temperate zones in the Northern hemisphere [1, 23]. Prominently in the previous three decades, anthelmintic resistance is reaching its peak and becoming a great issue in livestock development, and the resistance is being reported around the globe including South Pacific, Australia, Latin America, North America, Africa, Eastern Union, and Southeast Asia [23]. Several studies reporting the occurrence of antinematodal resistance against various chemotherapeutic agents residing in sheep abomasa from different parts of the world are shown in **Table 2**:

Hence, the growing anthelmintic resistance is threatening livestock production, increasing the toxic level in the environment, and ultimately reducing the food availability for human beings [23, 40]. Therefore, the scientists and parasitologists are performing the duty to raise one's hope by launching alternatives to overcome the developing resistance such as biological control (phytotherapy) [33].
