Animal Health, Economic Zoology, Snakes, Genetics and DNA Forensics

What to remember

• Zoonoses are diseases passed between animals and people. Forest staff meet rabies, anthrax, brucellosis, leptospirosis and Kyasanur Forest Disease, so safe handling and reporting are basic duties.
• Snakes: only four "Big Four" species cause most Indian bites (cobra, common krait, Russell's viper, saw-scaled viper). One polyvalent antivenom covers all four. Correct first aid is: keep the victim calm, immobilise the limb, go to hospital.
• Genetics and DNA: Mendel's ratios (3:1, 9:3:3:1), the Hardy-Weinberg equation, base pairing (A-T, G-C), PCR and STR profiling are the core ideas behind wildlife DNA forensics.

1. Animal health in forest areas

Wild animals, cattle grazing in forests and people share the same space. Disease can move between them. The forest officer's work is to spot early signs, isolate, report to the veterinary officer and protect staff.

Common signs of ill health in a wild animal: dull look, staying alone, loss of appetite, nasal or eye discharge, diarrhoea, limping, unusual behaviour, sudden deaths in a group.

Main diseases

Rinderpest, once a major killer of wild and domestic ruminants, has been declared eradicated worldwide.

Control measures

• Vaccinate cattle kept near protected areas (FMD, haemorrhagic septicaemia, black quarter) and village dogs (rabies, distemper).
• Quarantine sick animals and restrict movement of livestock.
• Burn or bury carcasses deep with lime. Wear gloves and a mask. Never cut open a suspected anthrax carcass.
• Collect samples properly. For histopathology, keep tissue in 10% formalin. For virus or bacterial tests, keep samples cool on ice. Send them with a clear record of date, place and species.
• Control ticks, flies and rodents around camps and elephant camps.

Immobilisation and rescue. Wild animals are tranquillised with a dart gun. Common drugs are xylazine, ketamine, tiletamine-zolazepam and the opioid etorphine. Opioids have antidotes (such as diprenorphine). Dose depends on body weight, so the weight is estimated first. Only trained veterinary staff should use these drugs. The animal is monitored for breathing and temperature, and kept in shade.

2. Economic zoology

Economic zoology studies animals that give useful products or services to people.

Honey bee society. One queen (fertile female, lays eggs), many workers (sterile females, do all the work) and a few drones (males, only to mate). Workers collect nectar and pollen and make honey. The rock bee builds a single large open comb on cliffs and tall trees. The Indian hive bee and the European bee nest in cavities and can be kept in boxes. Bees pollinate forest trees and crops.

Lac. The lac insect is a scale insect that sucks sap and secretes resin. Common host trees include palas (Butea monosperma), kusum and ber. Crude lac scraped from twigs is called stick lac; after cleaning it becomes seedlac, and after processing, shellac. Lac is a useful non-timber forest produce for tribal families.

Silk. Silk comes from the cocoon spun by the caterpillar. Mulberry silk is a domesticated silk. Tasar, eri and muga are wild or semi-wild silks, so they are linked with forest livelihoods. Andhra Pradesh is a notable silk-producing state (mulberry sericulture).

Other useful or harmful animals. Termites damage timber and seedlings. Mosquito fish (Gambusia) eat mosquito larvae and are used in biological control. Earthworms improve soil.

3. Snakes

All snakes are protected in India under wildlife law, and killing them is an offence. Snake knowledge helps forest staff in rescue and in treating bites.

Fang types (dentition)

Big Four venomous snakes

Other points: the king cobra (Ophiophagus hannah) is the longest venomous snake and eats other snakes. Vipers have a triangular head and vertical slit-like pupils. Venom glands are modified salivary glands. Snakes smell with the tongue and Jacobson's organ. Snakes are cold-blooded (ectothermic). The Indian rock python and rat snake are non-venomous.

Snakebite first aid

• 1. Keep the person calm and still. Fear speeds up the spread of venom.
• 2. Immobilise the bitten limb like a fractured limb, keeping it at heart level. Remove rings and tight items.
• 3. Wash the wound gently. Do not cut, suck, burn or apply a tight tourniquet. Do not give alcohol.
• 4. Take the person quickly to a hospital with antivenom. Note the time of the bite.
• 5. Antivenom is polyvalent: it works against the Big Four. It is given only in hospital.

4. Genetics

Mendel worked on the garden pea (Pisum sativum) and is called the father of genetics.

• Law of dominance: in a hybrid, only the dominant trait shows.
• Law of segregation (purity of gametes): the two alleles of a gene separate during gamete formation.
• Law of independent assortment: genes for different traits are inherited independently.

A test cross uses a recessive parent to find out whether an individual with the dominant trait is homozygous or heterozygous.

Other points. Codominance: both alleles show, as in AB blood group. ABO blood group is controlled by three alleles (IA, IB, i), an example of multiple alleles. Humans have 46 chromosomes (23 pairs); gametes have 23. In humans males are XY and females XX; in birds females are ZW. Colour blindness and haemophilia are X-linked recessive. A mutation is a sudden change in the DNA.

Hardy-Weinberg principle. In a large, randomly mating population with no selection, mutation or migration, allele frequencies stay constant: p + q = 1 and p² + 2pq + q² = 1. Worked example: if q² = 0.04, then q = 0.2, p = 0.8, and heterozygotes 2pq = 2 × 0.8 × 0.2 = 0.32.

5. DNA and wildlife forensics

DNA structure. Watson and Crick proposed the double helix (1953). Two strands are held by hydrogen bonds between bases: adenine pairs with thymine (2 bonds), guanine pairs with cytosine (3 bonds). In RNA, thymine is replaced by uracil. Chargaff's rule: A = T and G = C. Worked example: if adenine is 30%, thymine is 30%, and guanine = cytosine = 20%.

Central dogma: DNA → RNA (transcription) → protein (translation).

PCR (polymerase chain reaction) was developed by Kary Mullis. It copies a small amount of DNA millions of times in three repeated steps: denaturation (about 94-95 °C, strands separate), annealing (primers bind), extension (about 72 °C, Taq polymerase from the bacterium Thermus aquaticus adds bases). After n cycles one molecule gives up to 2ⁿ copies; after 5 cycles, 32 copies.

DNA fingerprinting was introduced by Alec Jeffreys. It compares repeating DNA sequences (VNTRs, now mostly short tandem repeats or STRs), which differ between individuals. Fragments are separated by gel electrophoresis; DNA moves toward the positive electrode because it is negatively charged.

Uses in forestry and wildlife work

• Identify the species of seized skin, bone, horn, ivory, meat or timber.
• Match a seized item to a poached animal, or link a poacher to a kill.
• Find the origin of ivory or a population of tigers by genetic mapping.
• Study population size and relationships from scat and hair samples.
• Mitochondrial genes such as cytochrome b and COI (barcoding) identify species, as mitochondrial DNA is abundant and survives in old samples.

Sample handling. Use gloves and clean tools. Collect blood, tissue, hair with root, feathers or scat. Keep samples dry or in absolute ethanol, cool, and in separate labelled bags. Keep a chain-of-custody record so the evidence is accepted in court. Indian centres known for DNA work include the Wildlife Institute of India (Dehradun) and CCMB / CDFD in Hyderabad.

Exam traps

• Cobra and krait venom is neurotoxic; viper venom is haemotoxic.
• Rinderpest is eradicated; FMD is still present.
• Tasar uses Antheraea mylitta; mulberry silk uses Bombyx mori; eri uses castor.
• The queen bee lays eggs; drones do not work; workers are females.
• A-T have 2 hydrogen bonds; G-C have 3.
• 3 : 1 is the phenotypic ratio of a monohybrid cross; 1 : 2 : 1 is the genotypic ratio.
• Test cross ratio 1 : 1 means the parent was heterozygous.
• Seedlac comes before shellac in lac processing.
• Never cut or suck a snakebite wound.
• Proteroglyphous = fixed front fangs; solenoglyphous = hinged hollow fangs.

One-liners

• 1. Rabies is caused by a virus and spreads through saliva of infected animals.
• 2. Anthrax is caused by Bacillus anthracis; carcasses must not be opened.
• 3. Surra is caused by Trypanosoma evansi.
• 4. Kyasanur Forest Disease is a tick-borne viral disease.
• 5. Etorphine is an opioid used to immobilise large wild animals.
• 6. Mulberry silkworm: Bombyx mori.
• 7. Apis dorsata is the rock bee.
• 8. Lac insect: Kerria lacca.
• 9. The Big Four snakes are cobra, krait, Russell's viper and saw-scaled viper.
• 10. Mendel worked on Pisum sativum.
• 11. Dihybrid phenotypic ratio is 9 : 3 : 3 : 1.
• 12. Taq polymerase works at about 72 °C in the extension step.

Practice questions

1. Rabies is caused by a virus of which genus?

   1. Pasteurella
   2. Lyssavirus
   3. Brucella
   4. Leptospira
   Answer

   B. Lyssavirus

   Rabies is a viral disease caused by Lyssavirus, spread through saliva.

2. A suspected anthrax carcass should NOT be:

   1. Buried deep with lime
   2. Reported to the veterinary officer
   3. Handled with gloves and mask
   4. Cut open for post-mortem in the field
   Answer

   D. Cut open for post-mortem in the field

   Opening the carcass releases spores that live long in soil.

3. Surra in elephants and camels is caused by:

   1. Pasteurella multocida
   2. Clostridium chauvoei
   3. Bacillus anthracis
   4. Trypanosoma evansi
   Answer

   D. Trypanosoma evansi

   Surra is a protozoan disease spread by biting flies.

4. Kyasanur Forest Disease is mainly spread by:

   1. Tsetse flies
   2. Ticks
   3. Rat fleas
   4. Culex mosquitoes
   Answer

   B. Ticks

   KFD is a tick-borne viral disease; monkey deaths are a warning sign.

5. Haemorrhagic septicaemia of cattle and buffalo is caused by:

   1. Clostridium chauvoei
   2. Trypanosoma evansi
   3. Pasteurella multocida
   4. Brucella abortus
   Answer

   C. Pasteurella multocida

   It is a bacterial disease caused by Pasteurella multocida.

6. Which animal disease has been declared eradicated worldwide?

   1. Anthrax
   2. Foot and mouth disease
   3. Rinderpest
   4. Brucellosis
   Answer

   C. Rinderpest

   Rinderpest was declared eradicated globally; FMD, anthrax and brucellosis still occur.

7. For histopathology, a tissue sample from a dead wild animal is best kept in:

   1. Vegetable oil
   2. Dry sand
   3. Plain tap water
   4. 10% formalin
   Answer

   D. 10% formalin

   10% formalin fixes tissue for microscopic study.

8. Which of the following drugs used in wildlife immobilisation is an opioid?

   1. Ketamine
   2. Etorphine
   3. Xylazine
   4. Diazepam
   Answer

   B. Etorphine

   Etorphine is an opioid with antidotes such as diprenorphine; the others are not opioids.

9. Consider the statements: 1. Rabies virus spreads through saliva of infected animals. 2. Anthrax is caused by a virus. Which is/are correct?

   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither 1 nor 2
   Answer

   A. 1 only

   Rabies spreads through saliva; anthrax is bacterial (Bacillus anthracis).

10. Silk obtained from silkworms fed on castor leaves is:

    1. Mulberry silk
    2. Muga silk
    3. Eri silk
    4. Tasar silk
    Answer

    C. Eri silk

    Eri silk comes from Samia ricini, which feeds on castor.

11. Which honey bee builds a single large open comb on cliffs and tall trees?

    1. Apis mellifera
    2. Apis florea
    3. Apis cerana indica
    4. Apis dorsata
    Answer

    D. Apis dorsata

    Apis dorsata is the rock bee, a single open-comb builder.

12. In a honey bee colony the egg-laying member is the:

    1. Worker
    2. Queen
    3. Drone
    4. Scout drone
    Answer

    B. Queen

    The queen is the only fertile egg-laying female; workers are sterile females.

13. Consider the statements: 1. Gambusia is used to feed on termites. 2. The lac insect is a scale insect that secretes resin. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Gambusia eats mosquito larvae; the lac insect (Kerria lacca) is a scale insect.

14. Which pair is correctly matched?

    1. Eri silk - Castor
    2. Muga silk - Mulberry
    3. Tasar silk - Samia ricini
    4. Vermiculture - Apis florea
    Answer

    A. Eri silk - Castor

    Eri silk comes from castor-fed Samia ricini; muga is Antheraea assamensis; vermiculture uses earthworms.

15. The raw lac scraped from twigs, after cleaning, is called:

    1. Shellac
    2. Stick lac
    3. Lac dye
    4. Seedlac
    Answer

    D. Seedlac

    Stick lac is cleaned to seedlac, which is processed into shellac.

16. Which snake has haemotoxic venom?

    1. Indian cobra
    2. Common krait
    3. Russell's viper
    4. King cobra
    Answer

    C. Russell's viper

    Vipers have haemotoxic venom; cobra, krait and king cobra are mainly neurotoxic.

17. A snake with a triangular head, vertical slit pupils and long hinged fangs is most likely a:

    1. Python
    2. Viper
    3. Rat snake
    4. Cobra
    Answer

    B. Viper

    Vipers are solenoglyphous with a triangular head and vertical pupils.

18. Hollow, long, folding front fangs are called:

    1. Proteroglyphous
    2. Opisthoglyphous
    3. Aglyphous
    4. Solenoglyphous
    Answer

    D. Solenoglyphous

    Solenoglyphous fangs belong to vipers; proteroglyphous are short fixed fangs (cobra, krait).

19. Which snake has a row of enlarged hexagonal scales along the back?

    1. Russell's viper
    2. Indian cobra
    3. Common krait
    4. Saw-scaled viper
    Answer

    C. Common krait

    The enlarged vertebral hexagonal scales are a feature of the common krait.

20. The correct first aid for a snakebite is to:

    1. Keep the person calm, immobilise the limb and go to hospital
    2. Tie a very tight tourniquet
    3. Cut the wound and suck out the venom
    4. Give alcohol to calm the person
    Answer

    A. Keep the person calm, immobilise the limb and go to hospital

    Cutting, sucking, tight tourniquets and alcohol are harmful; immobilise and reach antivenom quickly.

21. The Indian polyvalent antivenom acts against:

    1. King cobra, python, rat snake and keelback
    2. Cobra, python, sea snake and cat snake
    3. Krait, rat snake, sand boa and keelback
    4. Cobra, krait, Russell's viper and saw-scaled viper
    Answer

    D. Cobra, krait, Russell's viper and saw-scaled viper

    Polyvalent antivenom covers the Big Four.

22. The longest venomous snake, which feeds on other snakes, is the:

    1. King cobra
    2. Russell's viper
    3. Common krait
    4. Saw-scaled viper
    Answer

    A. King cobra

    Ophiophagus hannah is the king cobra.

23. Consider the statements: 1. Common krait venom is mainly neurotoxic. 2. Russell's viper venom is mainly haemotoxic. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Krait venom acts on nerves; Russell's viper venom acts on blood.

24. Mendel conducted his experiments on:

    1. Maize
    2. Garden pea
    3. Snapdragon
    4. Fruit fly
    Answer

    B. Garden pea

    Mendel used Pisum sativum.

25. The phenotypic ratio of a monohybrid cross (Tt x Tt) with complete dominance is:

    1. 9 : 3 : 3 : 1
    2. 1 : 2 : 1
    3. 1 : 1
    4. 3 : 1
    Answer

    D. 3 : 1

    Tt x Tt gives 3 dominant : 1 recessive.

26. In a cross Tt x Tt, the fraction of offspring that are homozygous recessive (tt) is:

    1. 3/4
    2. 1/2
    3. 1/4
    4. 1/8
    Answer

    C. 1/4

    Genotypes TT:Tt:tt = 1:2:1, so tt = 1/4.

27. In a dihybrid cross AaBb x AaBb, the probability of an aabb offspring is:

    1. 1/8
    2. 1/16
    3. 1/4
    4. 3/16
    Answer

    B. 1/16

    Each recessive homozygote is 1/4, so 1/4 x 1/4 = 1/16.

28. RrYy x RrYy gives 160 offspring. The expected number with both recessive traits (rryy) is:

    1. 10
    2. 20
    3. 30
    4. 40
    Answer

    A. 10

    rryy is 1/16 of 160 = 10.

29. A test cross Tt x tt produces 80 offspring. The expected number of tall (Tt) plants is:

    1. 80
    2. 40
    3. 60
    4. 20
    Answer

    B. 40

    Ratio is 1 Tt : 1 tt, so half of 80 = 40.

30. In a population, q2 = 0.09. The frequency of heterozygotes (2pq) is:

    1. 0.49
    2. 0.63
    3. 0.42
    4. 0.21
    Answer

    C. 0.42

    q = 0.3, p = 0.7, 2pq = 2 x 0.7 x 0.3 = 0.42.

31. In Hardy-Weinberg equilibrium p = 0.6. In a population of 500 the expected number of homozygous recessive individuals is:

    1. 80
    2. 120
    3. 60
    4. 200
    Answer

    A. 80

    q = 0.4, q2 = 0.16, 0.16 x 500 = 80.

32. In a DNA molecule adenine is 22%. The percentage of guanine is:

    1. 56%
    2. 22%
    3. 44%
    4. 28%
    Answer

    D. 28%

    A = T = 22%, so A+T = 44%; G = C = 56/2 = 28%.

33. The theoretical number of DNA copies after 6 PCR cycles from one starting molecule is:

    1. 128
    2. 12
    3. 64
    4. 36
    Answer

    C. 64

    Copies = 2^6 = 64.

34. A DNA stretch has 10 A-T pairs and 5 G-C pairs. The total number of hydrogen bonds is:

    1. 45
    2. 15
    3. 25
    4. 35
    Answer

    D. 35

    10 x 2 + 5 x 3 = 20 + 15 = 35.

35. The PCR step carried out at about 72 degrees C, in which Taq polymerase adds bases, is:

    1. Extension
    2. Denaturation
    3. Ligation
    4. Annealing
    Answer

    A. Extension

    Denaturation ~94 degrees C, annealing at lower temperature, extension ~72 degrees C.

36. In incomplete dominance, the F2 ratio of red : pink : white snapdragons is:

    1. 3 : 1 : 0
    2. 1 : 2 : 1
    3. 1 : 1 : 2
    4. 9 : 3 : 4
    Answer

    B. 1 : 2 : 1

    Heterozygotes show an intermediate pink colour, giving 1:2:1.

37. DNA fingerprinting was developed by:

    1. Gregor Mendel
    2. Erwin Chargaff
    3. Alec Jeffreys
    4. Kary Mullis
    Answer

    C. Alec Jeffreys

    Jeffreys developed DNA fingerprinting; Mullis developed PCR.

38. Taq polymerase used in PCR is obtained from the bacterium:

    1. Thermus aquaticus
    2. Agrobacterium tumefaciens
    3. Bacillus anthracis
    4. Escherichia coli
    Answer

    A. Thermus aquaticus

    Taq is heat-stable DNA polymerase from Thermus aquaticus.

39. A mitochondrial gene widely used for identifying species of seized wildlife parts is:

    1. Insulin gene
    2. Amylase gene
    3. Keratin gene
    4. Cytochrome b
    Answer

    D. Cytochrome b

    Mitochondrial genes such as cytochrome b and COI are used for species identification.

40. Consider the statements: 1. In RNA, thymine is replaced by uracil. 2. Guanine pairs with cytosine by two hydrogen bonds. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Statement 1 is correct. G-C pairs have three bonds, so statement 2 is wrong.

41. The documented record of who handled a seized sample at each stage, needed for court acceptance, is the:

    1. Sample plot
    2. Chain of custody
    3. Felling series
    4. Working circle
    Answer

    B. Chain of custody

    Chain of custody keeps evidence admissible.

42. A tissue sample from a poached animal is to be sent for DNA analysis. Best way to keep it is:

    1. Mixed with other samples in one bag
    2. In absolute ethanol, labelled and kept cool
    3. In 10% formalin for several months
    4. In open sunlight to dry
    Answer

    B. In absolute ethanol, labelled and kept cool

    Formalin damages DNA; ethanol or dry cool storage preserves it and separate labelled bags avoid contamination.

43. Consider the statements: 1. Anthrax is caused by a virus. 2. Rinderpest is still a widespread active disease worldwide. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    D. Neither 1 nor 2

    Anthrax is bacterial; rinderpest has been declared eradicated.

44. Consider the statements: 1. In a honey bee colony, drones are fertile males that mate with the queen. 2. Workers are fertile males. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Workers are sterile females; drones are males.

45. Consider the statements: 1. Mendel's law of segregation says the two alleles of a gene separate during gamete formation. 2. The dihybrid phenotypic ratio is 9 : 3 : 3 : 1. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are standard Mendelian results.