Parasites

Internal and external parasites are among the most common diseases we treat in backyard poultry. Most of our control efforts are geared towards reducing the number of infective stages in the environment and strategically using medications to help keep the parasites levels low inside the birds.

This section will cover the basics of the different internals and external parasites that are commonly found in New Zealand and how we can  develop a plan for managing them in our flocks.

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Internal Parasites

Almost every chicken that is raised in outdoor environment will have worms or other internal parasites. As long as the parasite numbers are low and your birds are in good condition, you will generally not see too many clinical problems from parasite infections.  However, the signs can be subtle and easy to miss so it’s important to do routine monitoring.

The best way to know if you’re birds are having a parasite problems is to send a sample of the droppings to a diagnostic laboratory to look for parasite eggs under the microscope.  If you are seeing visible worms (white, spaghetti-like threads or rice-grain like segments), changes in their droppings (diarrhoea, blood, mucus), or other clinical signs (weight loss, depression, pale comb, reduced egg production), then your chickens may already be heavily infected.

Types of Internal Parasites

There are three main classes of internal parasites that each require different drugs to treat them:

These include:

  • Hairworms (Capillaria) – small worms about 1.5 cm long that live in the crop. They use earthworms as part of their lifecycle.
  • Roundworms (Ascaridia)– large worms up to 7 cm long that live in the intestine causing inflammation and blockages.
  • Caecal Worms (Heterakis gallinarum) – generally does not cause problems on its own but can carry another parasite called Histomonas meleagridis (blackhead) that can cause more serious disease, particularly in turkeys.
  • Gapeworm (Syngamus trachea) – worms that live in the trachea (windpipe) causing gasping and head shaking in affected birds.

These segmented worms that can by anywhere from 5 mm to 25 cm long and live in the intestine. Depending on the species of tapeworm, they may have snails, beetles, flies, and slugs as part of the lifecycle. These are not very common in backyard poultry.

There are many different species that live in different parts of the intestinal tract. Almost every single bird in the flock will have coccidia, but it usually only becomes a problem if birds are exposed to a lot of coccidia oocysts (eggs) or the birds have a weakend immune system.

Parasite Life Cycles

Most of the parasites we treat are spread by chickens eating droppings or foraging in environments that contain infective eggs and/or larvae.

(1) Adult worms and coccidia live inside the birds and shed thousands of eggs into the environment usually through the droppings.

(2) Sometimes the eggs are directly infective to other birds and sometimes they need to mature into larvae before becoming infective.

(3)  Birds eat the eggs or larvae which then further develop into adult parasites that start shedding eggs (direct transmission).

(4) There are intermediate hosts (earthworms, snails, slugs, or beetles) that eat the eggs or larvae and then the birds eat the intermediate host to get infected (indirect transmission).

Once ingested, the eggs or larvae then develop into adult parasites inside the chicken to produce more parasite eggs

Controlling Internal Parasites

Parasite eggs and larvae tend to thrive when temperatures are between 10°C and 34°C.  If it’s too cold, many parasites become dormant and if it’s too hot, many parasites will start to die off. Unfortunately, the New Zealand climate tends to sit in the ideal range for parasites most of the year round.

The two main strategies for preventing or reducing problems with parasites are (1) reducing the number of worm eggs and larvae in the environment and (2) treating with deworming medications either strategically based on the results from a faecal egg count (preferred) or prophylactically at specific times of year.

Reducing worm eggs and larvae in the Environment

Here is a checklist of things you can try to get rid of infectious parasites in your flock’s environment:

Strategic Deworming

Strategic deworming is based on check faecal egg counts before treating your birds with any deworming products – this is when small sample of droppings from your flock is sent to a diagnostic laboratory where they will look at it under a microscope to tell you which parasites are present and how many parasite eggs are present to give you an idea of how heavily infected the birds are.

The best times to test are around Feb/Mar (autumn) just before birds are going into moult, Jun/Jul (late winter) just before birds are starting to lay again, and Sep/Oct (spring) when parasite burdens are likely to be highest. Birds should not have received any deworming medication within the previous month.

It is also good to re-check faecal egg counts 1 to 2 months after treatment to make sure the products worked.

It’s best is to grab two handfuls of droppings from under the roost in the morning, place it in a plastic bag, and mix it up to get a representative sample, You usually don’t want to mix droppings from more than 5 birds together in a single sample.

Depending on the findings, your veterinarian can help you develop a targeted medication plan to make sure birds are getting the right drug at the right dose at the right time. 

We usually only treat:

  • Roundworms or tapeworms if there are at least 800 to 1,000 eggs per gram of droppings 
  • Coccidia in adult birds if they have greater than 8,000 to 10,000 eggs per gram of droppings (or lower thresholds if the birds are showing clinical signs).

Prophylactic Deworming

Some flock owners choose to treat their birds prophylactically – meaning giving all birds in the flock worming medications at specific times of year (usually every 3 months) regardless of whether they are showing clinical signs or actually need it.  This is not ideal because it increases the chances of worms becoming resistant to the drugs and it can also be expensive to treat your flock when they don’t actually need it.

Deworming Medications

Formulation of Dewormers

Deworming medications come in three different formulations:

  • tablets or liquids that you give the birds directly into their mouth
  • already incorporated into pelleted feeds
  • concentrates that can be mixed into feed or water 

If your flock is small and the birds are easily handled, tablets or liquids are the best way to make sure everyone is getting the right dose of medication. Pelleted feed is also a relatively easy option since birds tend to eat a consistent amount every day. Medications given into feed or water are most often used in commercial farming systems where there is much greater control over what birds are eating and drinking.  If you just sprinkle the medications on top of your bird’s food or mix into their water containers, they may not get a high enough dose to kill off the worms.

Treating Nematodes (Roundworms)

The recommendations below are intended as general guidelines.  Please refer to the label of whichever product you are using to confirm the correct dosing instructions and with-holding periods.

Given at a dose of 20 – 36 mg/kg either directly by mouth or through water.  It is recommended to give a second dose 10 to 14 days after the first dose. Levamisole is labelled for use in chickens with 7 day with-hold period for eggs and 7 day with-hold period for meat.

Given at a dose of 20 – 30 mg/kg added to enough feed to last your flock for 7 days.  Flubendazole is labelled for use in chickens with 0 day with-hold period for eggs and 0 day with-hold period for meat.

Given at a dose of 20 – 50 mg/kg either directly by mouth or through water for 3 to 5 days with the same 3 to 5 day course repeated again in 10 to 14 days.  Fenbendazole is not labelled for use in chickens and so the recommended with-holding period is 10 days for eggs and 63 days for meat.

Given at a dose rate of 0.2 mg/kg either by mouth or applied topically. A second dose should be given 10 to 14 days after the first dose. Ivermectin is not labelled for use in chickens and so the recommended with-holding period is 10 days for eggs and 63 days for meat.

Given at a dose rate of 10 mg/kg either by mouth or through the water. A second dose should be given 10 to 14 days after the first dose. Oxfendazole is not labelled for use in chickens and so the recommended with-holding period is 10 days for eggs and 63 days for meat.

Give at a dose rate of 30 mg/kg by mouth daily for 3 days. Give a second 3 day course of treatment 10 to 14 days after the first. Mebendazole is not labelled for use in chickens and so the recommended with-holding period is 10 days for eggs and 63 days for meat.

Treating Cestodes (Tapeworms)

The recommendations below are intended as general guidelines.  Please refer to the label of whichever product you are using to confirm the correct dosing instructions and with-holding periods.

If using Droncit, give at a dose rate of 10 mg/kg by mouth. A second dose should be given 10 to 14 days after the first dose. Praziquantal is not labelled for use in chickens and so the recommended with-holding period is 10 days for eggs and 63 days for meat.

 

Treating Protozoa (Coccidia)

The recommendations below are intended as general guidelines.  Please refer to the label of whichever product you are using to confirm the correct dosing instructions and with-holding periods.

Give 20 mg/kg through their drinking water daily for 5 to 7 days. Amprolium is labelled for use in chickens with 10 day with-hold period for eggs and 5 day with-hold period for meat.

Give 7 mg/kg through their drinking water daily for 2 days. Toltrazuril should not be used in birds intended to produce eggs for human consumption and should not be used within 6 weeks of the start of a lying cycle. The recommended with-hold for meat is 16 days.

Give 1 g/L of drinking water daily for 2 days, then 3 days off, and 2 days on.  The recommended with-holding period is 10 days for eggs and 63 days for meat.

Withholding Times

When choosing a product, look to see what the medication withholding times are.  This is the number of days you have to wait before eating any eggs or meat from an animal that has been treated so that you are not consuming any of the drug that may still be in the bird’s system.

External Parasites

There are four main types of external parasites that can live on your backyard birds:

Scaly Leg Mites

Knemidocoptes mutans

Burrow under the skin on the legs causing the scales on the legs to become thickened, crusty, and lift away from the leg.

Red Mites

Dermanyssus gallinae

Become active at night and bite the skin of your birds to feed on their blood causing itchiness and anaemia (low red blood cell counts). These mites can survive in the environment for months.

Northern Fowl Mites

Ornithonysus sylviarum

Cause similar problems to red mites, but can only survive a few days without feeding on a chicken.

Lice

Menacanthus stramineus or Menopon gallinae

Feed on skin flakes and feather dander causing itching, feather damage, and skin irritation or infection.

Mites and lice most commonly get into your flock either through wild birds or buying new poultry that are already infected so good biosecurity is essential for keeping them out.  You also want to monitor your birds and coop closely for signs of infestations.

Lice lay eggs along the base of the feather shaft and are about the same size as sesame seeds. They are easiest to spot around the vent and tail feathers.  Mites often look like ground pepper and can be seen along the feather shaft and vane (soft part of feather). 

You may also start to notice red mites in the environment as well as on your chickens. The most common places are the nest boxes – you might actually feel them crawling up your arm when you pick up the eggs or they may look like tiny spots of blood on the eggs.  Red mites might also appear as small reddish clumps around roost bars and small cracks and crevices in the coop environment.