HEREDITARY NEUTROPENIA (TNS)
Hereditary neutropenia (or trapped neutrophil syndrome TNS) is a more recently described disease in Border Collies. Inheritance patterns and percentage of affected pups in litters indicate that TNS is inherited in a recessive manner (like CL) with both parents having to be carriers of the disease to produce an affected pup.
Symptoms may be seen in puppies as young as 2 weeks or as old as 7 months of age. Affected puppies are usually smaller, have slower growth rates, and can appear to have a “ferret like” head and a poor hair coat. Some puppies are not obviously different until they become ill. Other symptoms of disease include lameness, inappetence, diarrhoea and a high temperature. .
Xrays of limb bones may show reduced density and thin cortices and in some cases fractures in metaphyses. Sometimes pups become ill after their first vaccination. Both male and female puppies of any colour can be affected. TNS is a disease which ultimately causes a deficiency of the immune system, so symptoms can vary between pups. Affected animals are eventually euthanased on humane grounds.
Diagnosis of TNS requires three criteria. Firstly, the pups need to show clinical symptoms consistent with the TNS. Secondly, blood tests which confirm a low neutrophil count are suspicious of TNS but do not provide a diagnosis. Puppies will occasionally develop low neutrophil counts for other reasons, eg. viral or bacterial infections, and should not be condemned on this basis. The third criteria bone marrow biopsy will give accurate diagnosis. Pups with TNS have
been found to have an increased “myeloid to erythroid ratio” in their bone marrow. This means there are more white blood cells precursors in the bone marrow than there should be hence the name “trapped neutrophil syndrome” (
neutrophils trapped in the bone marrow) was made.
For pet owners it should be emphasised that: 需要对犬主强调的是：
1. Only a small number of TNS litters have been reported to date. This problem is often detected by breeders before sale of the litter.
2. Carrier puppies live perfectly normal, healthy and will never show any symptoms of TNS. However carrier animals should not be used in breeding programs.