A method of detecting avian necrotic enteritis, in particular sub-clinical avian necrotic enteritis, wherein detection of necrotic enteritis is carried out by detecting the amount of at least one of the following sequences in an avian sample: a) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 40, preferably at least 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 1, b) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 20, preferably at least 25, 40, 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 3, c) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 20, preferably at least 25, 40, 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 4; d) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 20, preferably at least 25, 40, 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 7; e) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 20, preferably at least 25, 40, 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 9; f) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 8 or 10, preferably at least 12, 14, 16, 18, 20, 25, 40, 60 or 80, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 10; g) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 8 or 10, preferably at least 12, 14, 16, 18, 20, 25, 40 or 60, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 11; h) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 8 or 10, preferably at least 12, 14, 16, 18, 20, 25, 40 or 60, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 12; i) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 8 or 10, preferably at least 12, 14, 16, 18, 20, 25, 40 or 60, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 13; j) polynucleotides (DNAs and RNAs) which are complementary to the sequences according to (a) to (i); k) polynucleotides (DNAs and RNAs) which are complementary to the sequences according to (j); l) polynucleotides which comprise the polynucleotides according to (a) to (k). a) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 40, preferably at least 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 1, b) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 20, preferably at least 25, 40, 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 3, c) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 20, preferably at least 25, 40, 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 4; d) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 20, preferably at least 25, 40, 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 7; e) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 20, preferably at least 25, 40, 60, 100, 150, 180 or 200, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 9; f) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 8 or 10, preferably at least 12, 14, 16, 18, 20, 25, 40, 60 or 80, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 10; g) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 8 or 10, preferably at least 12, 14, 16, 18, 20, 25, 40 or 60, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 11; h) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 8 or 10, preferably at least 12, 14, 16, 18, 20, 25, 40 or 60, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 12; i) polynucleotides which have a sequence identity of at least 95 %, preferably 100 %, to a polynucleotide which consists of at least 8 or 10, preferably at least 12, 14, 16, 18, 20, 25, 40 or 60, consecutive nucleotides of the nucleotide sequence as depicted in SEQ ID NO: 13; j) polynucleotides (DNAs and RNAs) which are complementary to the sequences according to (a) to (i); k) polynucleotides (DNAs and RNAs) which are complementary to the sequences according to (j); l) polynucleotides which comprise the polynucleotides according to (a) to (k).