Prevalence and genetic evolution of porcine reproductive and respiratory syndrome virus in commercial fattening pig farms in China

Table 1 Pig farms information

Name	Farming scale	Vaccination	Monitoring time	Death rate (%)	Sample size	Number of positive samples	Positive rate (%)	Subtypes
Heilongjiang A farm	1000	No vaccination	2020	1.60	180	38	36.58	L1.8(L1C) PRRSV
Heilongjiang B farm	3400	CH-1R MLV^a	2020	12.09	283	82	29.33	L1.8(L1C) PRRSV, L1.5(L1A) PRRSV, L8.7(L8E, HP-PRRSV-like PRRSV), L8.7(L8E, CH-1a-like PRRSV) and L3.5(QYYZ-like PRRSV)
Heilongjiang C farm	4000	HuN4-F112 MLV^b	2020–2021	5.55	239	107	44.77	L1.8(L1C) PRRSV and L8.7(L8E, HP-PRRSV-like PRRSV)
Henan farm	500	No vaccination	2020	4.00	132	38	28.79	PRRSV-1, L8.7(L8E, HP-PRRSV-like PRRSV), L1.8(L1 C) PRRSV and L5.1(L5A, ATCC-VR2332-like PRRSV)
Xinjiang farm	1400	No vaccination	2020	16.86	236	91	38.56	L1.8(L1C) PRRSV and L8.7(L8E, HP-PRRSV-like PRRSV)
Hebei farm	2000	No vaccination	2020–2021	24.50	270	144	53.33	L1.8(L1C) PRRSV and L1.5(L1A) PRRSV
Hubei farm	2000	TJM MLV^c	2020–2021	2.49	57	10	17.54	L8.7(L8E, HP-PRRSV-like PRRSV)

^aEach about 60-day-old piglet were vaccinated intramuscularly 1 dose (2 ml) with CH-1R MLV
^bEach about 60-day-old piglet were vaccinated intramuscularly 1 dose (2 ml) with HuN4-F112 MLV
^cEach about 15-day-old piglet were vaccinated intramuscularly 0.5 dose (1 ml) with TJM MLV

ISSN: 2055-5660