Selection of Pigs to Submit to the Lab:

Anytime you choose to send pigs to the laboratory several steps need to be followed:

Step 1:

You need to have a list of potential causes of the problem before submitting pigs to the lab. The list is developed by examining pigs at the farm and determining the clinical pattern of the disease. A veterinary consultant with experience in swine production is capable of assisting in this process and can direct the lab work. The history of the problem in your herd is important. For example, how many previous groups of pigs have exhibited the same problem? Is there a seasonal pattern to the problem? What do your production records reveal about the seriousness of the problem? Some problems are diagnosed with relative certainty at the farm. Pigs with gastric ulcers or "bleach-outs" are easily recognized at the farm by their pale color, thin body condition, and weak, wobbly step due to being off-feed. What is not easily recognized is any underlying problem such as pneumonia or scours which may accompany the ulcer. Some clinical problems such as piglet scours require laboratory tests to confirm the cause. Piglet scours has many causes and include transmissible gastroenteritis (TGE) virus, rotavirus, E. coli or colibacillosis, Clostridium perfringens types A and D, coccidiosis and others. The age of the piglets which are affected, the number of pigs affected, the color and consistency of the feces, the number of pigs which have died, and the response of pigs to treatment are observations which are helpful in determining the cause of the scour. Management factors which are detected at the farm include chilling of pigs either by wet conditions, drafts, or temperatures which are either too low or which vary from high to low. While these factors are not the cause of the problem they certainly stress the pigs and create the situation for the pigs to get sick. Coughing pigs in the nursery or finishing is another example of a disease which requires lab tests to determine the cause(s). Mycoplasmal pneumonia, Pasteurella pneumonia, Streptococcal sp. pneumonia, Hemophilus parasuis (Glasser's), porcine reproductive and respiratory virus (PRRSV), pseudorabies virus (PrV), swine influenza virus (SIV), and porcine respiratory coronavirus (PRCV) are all capable of causing pneumonia. Serology or blood tests for antibodies to these pathogens, selected pigs for laboratory testing, and slaughter examination of lungs on market weight pigs are some methods to diagnose the cause(s).

Step 2.

The pigs to select will depend upon the type of problem in the herd, for example if the problem is suckling piglet diarrhea then piglets that are just starting to scour need to be submitted. If the problem is coughing pigs in the finishing, then serum samples along with a few chosen pigs in finish are selected to be submitted to the lab. If the problem is sows failing to farrow, then serum or urine samples, swabs for microbiologic examination, and possibly a select sample of sows will be submitted to the lab for post mortem depending upon the seriousness of the problem. Examination of reproductive tracts at slaughter is another possible method to identify the problem. Diarrhea in finishing pigs is a challenge to diagnose without sacrificing pigs. Identification of salmonellosis or proliferative enteritis (ileitis) requires examination of the pig at the lab and further laboratory tests including culture, histopathology, polymerase chain reaction (pcr), or other newer diagnostic methods.

Step 3.

Pigs which have died or are found dead in the morning are usually not good specimens to submit to the lab. These pigs may be suitable for posting at the farm by one trained in pathology and diagnosis. The problem with dead pigs is that they may yield bacteria which grew after the pig died and are not the real cause of death. Also the internal tissues such as the intestinal tract will decompose quickly once the pig dies. This is especially true in hot weather. Any lab results from pigs which have died are difficult to interpret and may be misleading. Pigs which are thin, gaunt, dehydrated and which have been treated with antiinfectives are poor specimens to submit to the lab. Pigs which have been treated with antiinfectives may fail to yield the cause of the problem. Antiinfectives may reduce or eliminate the bacteria that caused the problem making it difficult to isolate them at the lab. Whatever bacterium is isolated at the lab may not be the real cause of the problem. Pigs which are just becoming sick are more likely to yield bacteria causing the problem since they are carrying large numbers of the bacterial organisms. Pigs receiving antiinfectives is a confounding problem for the diagnosis since virtually all pigs which are submitted to the lab have been treated with antiinfectives either in feed, water, or by injection. The result is that one must determine if the problem is serious enough to use the lab and if so, then pigs must be submitted prior to the antiinfectives being used in feed, water, or by injection. This rarely happens. Examples of antiinfectives include apramycin, bacitracin, carbadox, ceftiofur, chlortetracycline, gentamicin, lincomycin, neomycin, oxytetetracycline, penicillin, tetracycline, tiamulin, tribrissen, tylosin, spectinomycin, and various sulfonamides, to name just a few.

Step 4.

A complete history of the problem including all clinical signs such as coughing, difficult breathing, diarrhea, sneezing, lameness, discharges, abortions, mummified fetuses, reduced feed intake, reduced water intake, and any other important signs should be written onto the laboratory submission form. In addition, all water, feed, or injectable antiinfectives (antibiotic) which have been given to the pigs should be indicated on the lab form. Include the number of days treated, the dose, the name of the antiinfective, how the pigs have responded, the number of pigs affected, the age of pigs affected, the number of pigs which died, the number of pigs which are growing poorly, and any other pertinent information. This details the problem for the pathologist at the lab and it aids in the interpretation of the lab result when completed.

Step 5.

Deliver the pigs promptly to the laboratory. Live pigs should be taken quickly to insure their survival at the laboratory.

Take-Home Message

Five steps to remember when submitting pigs to the lab:

Step 1: Have an idea what the problem is in the herd and submit samples which are appropriate. Seek professional help to determine the best plan of action.

Step 2: Pigs to submit will be determined by the problem in the herd.

Step 3: Pigs found dead or pigs which have received antiinfectives are not the best specimens to submit to the lab.

Step 4: Include a complete history when submitting the pigs to the lab. This helps the pathologist and provides you with a written record of the problem.

Step 5: Deliver pigs promptly to the laboratory.

Selection of Antiinfectives (Antibiotics):

Antiinfectives include both antibiotics and chemical compounds which are used to combat bacterial, fungal, and protozoal infections. Antibiotics are derived from the fermentation of living organisms found in the soil while antiinfectives are chemical compounds which can be synthesized in the laboratory. Antiinfectives do not have any effect on viral infections. Ideally, the infectious agent being treated will be susceptible to the antiinfective selected for use. After successfully isolating the bacterium at the laboratory, a susceptibility test can be done. Specifically, if it is diarrhea caused by Salmonella cholerae suis, then we want an antiinfective which is active against Salmonella cholera suis. If it is pleuropneumonia caused by Actinobacillus pleuropneumoniae, then an antiinfective which is active against A. pleuropneumoniae is desired. The route of administration will vary. Medicating large numbers of pigs with minimal labor requires either an in-feed or in-water route of administration. Unfortunately, when pigs become sick, daily feed intake decreases and water intake may also be less. If pigs do not eat or drink, then they do not receive the daily dose of medication. We may believe that the antiifective is not working when it is the route of administration that is wrong. Another concern with some antiinfectives in water is that they are bitter and pigs refuse to drink. Treating pigs in feed or water must always be supplemented with individual pig treatments by injection or oral dosing to provide medication to those pigs who are not eating or drinking fully. Early detection and treatment with an appropriate antiinfective is critical for success of the treatment. Once pigs become chronic or sick over 4-5 days, then they do not respond favorably to treatment by any route of administration. Certain antiinfective are not absorbed from the gastrointestinal tract and therefore are of little value in treating generalized infections in the pig's body.

group of antiinfectives: TETRACYCLINES
examples of this group include: tetracycline, chlortetracycline, oxytetracycline
characteristics of this group: broad spectrum, gram positive and negative, eperythrozoonosis, interfere with protein synthesis therefore bacteriostatic, respiratory infections particularly Pasteurella multocida, oral treatment results in a peak blood level in 2-4 hours after starting the medication

group: AMINOGLYCOSIDES
examples: gentamicin, neomycin, streptomycin (aminocyclotol)
characteristics: spectrum is mainly gram negative, enteric infections like E. coli, salmonellosis, resistance does occur, resistance to one member may mean resistance to another member, potentially toxic to the nervous, respiratory, and cardiovascular systems, do not exceed the recommended dosage

group: PENICILLINS
examples: procaine penicillin G, benzathine penicillin, ampicillin
characteristics: spectrum is mainly gram-positive, act on bacterial cell wall synthesis, safe, relatively non-toxic, used for streptococcal and staphylococcal infections, erysipelas, actinomyces and increasingly for pneumonias associated with pasteurella.

group: MACROLIDES
examples: tylosin, erythromycin
characteristics: spectrum is mainly gram positive, Mycoplasma hyosynoviae (arthritis)

group: SULFONAMIDES
examples: sulfadimethoxine, sulfathiazole, sulfamethazine, sulfapyridine
characteristics: spectrum is both gram-positive and gram-negative, used for both enteric and respiratory infections (atrophic rhinitis), action is through competitive inhibition of para-aminobenzoic acid which is required by bacteria for the formation of folic acid for the subsequent production of purines and nucleic acids, residues of feeders or waterers must be avoided to reduce the risk of residues in carcasses, some sulfas are bitter-tasting

others: Lincomycin, distinct from macrolides, but the same spectrum, swine dysentery, mycoplasmosis

Water Therapy:

Medicating pigs via the water requires that a system is in place at the herd. Two primary types of water medicating systems are utilized. A batch system has a large bulk tank in which the drug is mixed. This solution is then the only source of drinking water for the pigs. Correctly mixed drugs in this system allow for accurate administration of drugs to the pigs. Additionally a determination of water consumption can be estimated by the rate of disappearance of water from the tank. A second system uses a proportioning device. This device allows for a stock solution to be mixed into a tank and then the proportioner delivers a set amount of drug into the water supply for the unit. The proportioner can deliver the appropriate amount of drug if properly maintained and kept free from obstruction. Drugs which are thick and do not flow easily may be a problem in a proportioner system.

The amount of drug to be administered into each pig is based upon the dose plus the weight of the pig. When calculating the amount of drug to use both of these factors must be considered. In addition, the daily intake of water by each pig will influence the amount of drug received. Theoretically, each pig will have free access to water; however, anything which decreases the pig's willingness to drink such as sickness or bitter tasting water will decrease the dose of medication the pig receives. The effect of heavy mineralized water has not been fully determined; however, the potential is real for some minerals to tie up antiinfective drugs and keep them from being absorbed in the intestinal tract.

To determine the dose of a drug to be used always follow the directions on the label.

• Figure the total number of pounds of pork to treat.
• multiply this total number of pounds by the dose which is mg per pound
• total mg of drug needed
• dissolve this amount in water
• maintain this level of drug in the water for at least 5-7 days
• pigs normally consume water at 10 % of their body weight per day
• this level will increase when the weather is hot (15% of their body weight)
• pigs on medicated water will consume somewhat less

Example:

• assume 1000 pigs in finishing weighing an average of 100 lb
• the drug needed to treat these pigs would be calculated by figuring the total number of pounds of pork to treat (100,000 lb) times the dose (10 mg / lb)=1,000,000 mg = 1000gm of drug / day
• this amount is then mixed into solution with water.
• maintain this amount in the water for 5-7 days. One problem is failing to treat pigs the right length of time perhaps resulting in an increase in bacterial populations which are resistant to the drug being used.

Medicating large numbers of pigs via in the water is desirable since it reduces labor and stress on both the pigs and the workers. Unfortunately, severely-sick pigs may consume less water depending upon the illness. Pigs that drink less water will not take in a full dose of medicine. Also, piglets nursing sows will not consume enough water to ingest a therapeutic level of medication. Illnesses such as these will require individual pig treatments either by injection or oral dosing. When treating pigs from between weaning to market, water medication is useful, but the sickest pigs still need to be injected with the appropriate antiinfective and separated into a separate "hospital pen" to insure easy access to feed and water and to minimize the fighting among pen-mates. In some instances, supplemental heat lamps are suggested to provide adequate warmth for these sick pigs.

Take-Home Message

1. Water therapy requires a medicating system at the farm and routine maintenance of the system to be certain that it is not plugged or malfunctioning.