Fleas, ticks and worms: complete prevention

Parasites are the #1 cause of avoidable vet visits. A good preventive routine costs €5-15 a month and avoids bigger problems: anaemia from fleas, serious tick-borne diseases (ehrlichiosis, babesiosis) or zoonotic worms. This guide covers complete prevention.

External parasites: fleas and ticks

Fleas (Ctenocephalides canis and felis): jumping insects of 2-3 mm that live in the dog's coat and feed on its blood. One female lays up to 50 eggs a day. In 2 weeks you have a serious infestation at home.

Ticks (Rhipicephalus, Ixodes, Dermacentor): arachnids that attach to the skin and suck blood for days. They transmit canine ehrlichiosis, anaplasmosis, babesiosis and Lyme disease. Some can also bite humans.

How to tell if your dog has parasites

Fleas - signs:

• Intense scratching (especially the base of the tail, neck, belly)
• Coat with "black dust" at the base (flea dirt, turns reddish when wet)
• Mood changes: irritability from constant discomfort
• Pale gums (anaemia in severe cases, especially puppies)

Ticks - signs:

• Feel over the body after walks: look for hard little lumps attached to the skin
• Favourite spots: ears, neck, armpits, groin, between the toes
• Once fed, it looks like a grape or a bean. Before that it looks like a small seed.

Spot-ons

Spot-ons are applied on the scruff + base of the tail (areas the dog can't lick). They work by spreading over the skin through skin oils for 4 weeks (some 12). Main brands:

• Frontline Tri-Act: fleas + ticks + mosquitoes. 4 weeks. €10-15/spot-on. Top choice among vets.
• Advantix: similar, also with permethrin (TOXIC to cohabiting cats). €10-15.
• Bravecto Spot-On: 12 weeks (4x longer). €30-40/spot-on.
• Effipro Duo / Frontline Combo: mid-range price, no mosquito repellent. €5-10/spot-on.

Apply with the dog dry. Don't bathe for 48h afterwards. Don't stroke the application area for 12h.

Anti-parasite collars

The best known and most effective are Scalibor (deltamethrin) and Seresto (imidacloprid + flumethrin). They release the active ingredient steadily for 6-8 months.

• Seresto: 8 months · €50-70 · fleas + ticks. Considered the most effective. Starts working within 24-48h.
• Scalibor: 6 months · €25-35 · fleas + ticks + sandflies (the leishmaniasis mosquito). Recommended in Mediterranean areas.

Advantages: you don't think about it, and it doesn't come off with baths. Disadvantages: if your dog swims a lot (sea/river), it loses some effectiveness — reinforce with a spot-on every 8 weeks.

Tablets (oral)

Chewable tablets that act from the inside. Useful for dogs that react to spot-ons or collars:

• NexGard: 1 month · €8-12 · fleas + ticks. Chicken flavour, palatable.
• Simparica / Simparica Trio: 5 weeks · €10-15. The Trio includes internal parasites (not for pregnant bitches).
• Bravecto Oral: 12 weeks · €25-35. Very practical (4 tablets a year cover everything).

Advantage: it works even if the dog swims. Disadvantage: higher cumulative annual cost than a budget spot-on.

Internal parasites: worms

The most common ones:

• Roundworms (Toxocara canis): a 10-20 cm worm. Puppies are often born infected (transplacental transmission).
• Hookworms (Ancylostoma caninum): a smaller worm that attaches to the intestine and causes anaemia.
• Whipworms (Trichuris vulpis): causes diarrhoea with mucus/blood.
• Tapeworms (Dipylidium caninum, Echinococcus): flatworms. Transmitted by fleas or raw meat.
• Giardia: a protozoan that causes intermittent watery diarrhoea.

A broad-spectrum dewormer at least 4 times a year (every month if the risk is high): for example Drontal Plus or Milbemax. Cost: €3-8 per tablet depending on weight.

Leishmaniasis (sandfly)

In endemic areas (the Mediterranean coast, Andalusia, Extremadura, Aragon, Madrid, the Balearic Islands…) sandflies transmit canine leishmaniosis from April to November at the very least, and all year round in warm areas. It is a chronic disease that can appear years after infection; with early diagnosis and treatment, many dogs live a normal life. Dogs do not pass it directly to people.

Comprehensive protection:

• Annual vaccine (Letifend), from 6 months of age and after a negative test — it reduces the risk of developing the disease if infected
• Anti-sandfly collar (Scalibor) throughout the warm season
• Spot-ons with permethrin (Advantix, Frontline Tri-Act) — repellent efficacy
• Annual test in an endemic area, from 6-12 months of age and always before vaccinating, to detect infection in time

If your dog lives permanently in an endemic area, the combination of a Scalibor collar + annual vaccine is the most advisable.

Heartworm disease

It is caused by Dirofilaria immitis, a worm that lodges in the heart and pulmonary arteries. It is transmitted by common mosquitoes (Culex, Aedes). In Spain it is endemic in the Canary Islands, the Levante, Huelva and Doñana, and in irrigated valleys (Ebro, Guadalquivir, Tagus, Salamanca).

Prevention: a monthly tablet (Milbemax, Heartgard) or monthly spot-on (Advocate) during the mosquito season (all year round in the Canary Islands and warm areas; spring to autumn elsewhere).

Cost: €3-5/tablet. Vital in risk areas — the curative treatment is expensive, long and dangerous.

Frequency by area and season

Mediterranean / eastern Spain / southern Spain / Canary Islands:

• External: MONTHLY spot-on or a Seresto/Scalibor collar all year round
• Internal: at least 4 times a year (every month for puppies or dogs that eat faeces)
• Leishmaniosis: repellent (collar or spot-on) from April to November, or all year round if it is warm + annual vaccine with a prior test if your vet recommends it
• Heartworm: monthly preventive all year round in the Canary Islands; elsewhere, during the mosquito season

Northern / continental areas:

• External: MONTHLY spot-on March-November · every two months December-February
• Internal: at least 4 times a year
• Leishmaniasis: NOT necessary unless you travel to the Mediterranean
• Heartworm: ask your vet if you live near rivers or irrigated areas

Pregnant bitches and puppies

Pregnant dog: each product has its own conditions during pregnancy and lactation; some are authorised and others are not. Always ask your vet which one to use and when (for example, internal deworming at the end of pregnancy to protect the puppies).

Puppies 0-8 weeks: internal deworming at 2, 4, 6 and 8 weeks with a paediatric product (Drontal Junior). Do NOT use spot-ons/collars before 2 months.

Puppies 2-6 months: MONTHLY internal and external routine (their immune system is still developing).

If it already has parasites: treatment

If you find fleas:

1. Rapid-attack treatment: spot-on + an environmental spray such as Indorex throughout the WHOLE house
2. Wash the dog's bed at 60°C + vacuum thoroughly (eggs, larvae)
3. Repeat after 4 weeks (the flea cycle is 14-21 days)
4. Keep up the monthly preventive routine for 6 months

If you find a tick:

1. Remove with fine tweezers, grip close to the skin, pull straight and firm (without twisting)
2. Disinfect the area
3. Apply external parasite protection if it wasn't wearing any
4. Watch for 2-3 weeks for symptoms: fever, apathy, loss of appetite (a sign of a transmitted disease)
5. If symptoms → vet with a blood sample to test for ehrlichia/anaplasma/babesia

If it has worms: consult the vet to identify the species through a faecal test and give the right dewormer (not all cover everything). Repeat the treatment after 2 weeks to kill any adult forms that escaped the first attack.

In short: parasite control is non-negotiable: external according to the duration of the product and internal at least 4 times a year. Cost €5-15 a month · it avoids bigger problems. Adjust to your area (more protection on the Mediterranean and in heartworm areas). On Mizuu you can record the parasite control schedule in your dog's digital passport and receive alerts when the next dose is due.